diff --git a/contract/marketplace.abi.json b/contract/marketplace.abi.json
deleted file mode 100644
index ef509c3e..00000000
--- a/contract/marketplace.abi.json
+++ /dev/null
@@ -1,110 +0,0 @@
-[
-	{
-		"inputs": [
-			{
-				"internalType": "uint256",
-				"name": "_index",
-				"type": "uint256"
-			}
-		],
-		"name": "buyProduct",
-		"outputs": [],
-		"stateMutability": "payable",
-		"type": "function"
-	},
-	{
-		"inputs": [],
-		"name": "getProductsLength",
-		"outputs": [
-			{
-				"internalType": "uint256",
-				"name": "",
-				"type": "uint256"
-			}
-		],
-		"stateMutability": "view",
-		"type": "function"
-	},
-	{
-		"inputs": [
-			{
-				"internalType": "uint256",
-				"name": "_index",
-				"type": "uint256"
-			}
-		],
-		"name": "readProduct",
-		"outputs": [
-			{
-				"internalType": "address payable",
-				"name": "",
-				"type": "address"
-			},
-			{
-				"internalType": "string",
-				"name": "",
-				"type": "string"
-			},
-			{
-				"internalType": "string",
-				"name": "",
-				"type": "string"
-			},
-			{
-				"internalType": "string",
-				"name": "",
-				"type": "string"
-			},
-			{
-				"internalType": "string",
-				"name": "",
-				"type": "string"
-			},
-			{
-				"internalType": "uint256",
-				"name": "",
-				"type": "uint256"
-			},
-			{
-				"internalType": "uint256",
-				"name": "",
-				"type": "uint256"
-			}
-		],
-		"stateMutability": "view",
-		"type": "function"
-	},
-	{
-		"inputs": [
-			{
-				"internalType": "string",
-				"name": "_name",
-				"type": "string"
-			},
-			{
-				"internalType": "string",
-				"name": "_image",
-				"type": "string"
-			},
-			{
-				"internalType": "string",
-				"name": "_description",
-				"type": "string"
-			},
-			{
-				"internalType": "string",
-				"name": "_location",
-				"type": "string"
-			},
-			{
-				"internalType": "uint256",
-				"name": "_price",
-				"type": "uint256"
-			}
-		],
-		"name": "writeProduct",
-		"outputs": [],
-		"stateMutability": "nonpayable",
-		"type": "function"
-	}
-]
\ No newline at end of file
diff --git a/contract/propertyMarketplace.sol b/contract/propertyMarketplace.sol
index 296b4cdd..b5bdeeb0 100644
--- a/contract/propertyMarketplace.sol
+++ b/contract/propertyMarketplace.sol
@@ -5,28 +5,45 @@ pragma solidity >=0.7.0 <0.9.0;
 import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
 
 contract HouseToken is ERC20 {
-    constructor(string memory tokenName, string memory symbol, uint supply, address owner) ERC20(tokenName, symbol) {
-        _mint(owner, supply * 10 ** decimals());
+    constructor(
+        string memory tokenName,
+        string memory symbol,
+        uint supply,
+        address owner
+    ) ERC20(tokenName, symbol) {
+        _mint(owner, supply * 10**decimals());
     }
 }
 
-
 interface IERC20Token {
-  function transfer(address, uint256) external returns (bool);
-  function approve(address, uint256) external returns (bool);
-  function transferFrom(address, address, uint256) external returns (bool);
-  function totalSupply() external view returns (uint256);
-  function balanceOf(address) external view returns (uint256);
-  function allowance(address, address) external view returns (uint256);
-
-  event Transfer(address indexed from, address indexed to, uint256 value);
-  event Approval(address indexed owner, address indexed spender, uint256 value);
+    function transfer(address, uint256) external returns (bool);
+
+    function approve(address, uint256) external returns (bool);
+
+    function transferFrom(
+        address,
+        address,
+        uint256
+    ) external returns (bool);
+
+    function totalSupply() external view returns (uint256);
+
+    function balanceOf(address) external view returns (uint256);
+
+    function allowance(address, address) external view returns (uint256);
+
+    event Transfer(address indexed from, address indexed to, uint256 value);
+    event Approval(
+        address indexed owner,
+        address indexed spender,
+        uint256 value
+    );
 }
 
 contract PropertyMarketplace {
-
-    uint internal propertiesLength = 0;
-    address internal cUsdTokenAddress = 0x874069Fa1Eb16D44d622F2e0Ca25eeA172369bC1;
+    uint private propertiesLength = 0;
+    address internal cUsdTokenAddress =
+        0x874069Fa1Eb16D44d622F2e0Ca25eeA172369bC1;
 
     struct Property {
         address payable owner;
@@ -38,14 +55,14 @@ contract PropertyMarketplace {
         HouseToken houseToken;
     }
 
-    struct PropertyLabel{
+    struct PropertyLabel {
         string name;
         string image;
         string description;
         string location;
     }
 
-    struct PropertyStockData{
+    struct PropertyStockData {
         uint price;
         uint sold;
         uint numShares;
@@ -57,23 +74,57 @@ contract PropertyMarketplace {
         SoldOut
     }
 
-    mapping (uint => Property) internal properties;
-
- 
+    mapping(uint => Property) internal properties;
+    mapping(uint => bool) private exists;
 
+    /// @dev checks if a property exist
+    modifier exist(uint _index) {
+        require(exists[_index], "Query of non existent property");
+        _;
+    }
+    /// @dev checks if caller is the property owner
+    modifier onlyPropertyOwner(uint _index) {
+        require(properties[_index].owner == msg.sender, "Unauthorised caller");
+        _;
+    }
+    /// @dev checks if any property's shares have been sold
+    modifier onlySharesNotSold(uint _index) {
+        require(
+            properties[_index].stockData.sold == 0,
+            "The sale cannot be updated if some tokens are already issued"
+        );
+        _;
+    }
+    /// @dev checks if sale of property has been cancelled
+    modifier isNotCancelled(uint _index) {
+        require(
+            properties[_index].status != Status.SaleCancelled,
+            "The property sale is cancelled"
+        );
+        _;
+    }
 
+    /// @dev creates a property
     function writeProperty(
-        PropertyLabel memory _label, 
+        PropertyLabel calldata _label,
         PropertyStockData memory _stockData,
         uint _bedrooms,
         uint _bathrooms
     ) public {
-        uint _sold = 0;
-        _stockData.sold = _sold;
-        
+        _stockData.sold = 0;
+        require(
+            _stockData.numShares > 0,
+            "Number of shares needs to be at least one"
+        );
+        require(_stockData.price > 0, "Invalid share price");
         //create a house token - there will be as many tokens as there are shares to be sold
-        HouseToken _houseToken = new HouseToken(_label.name, "HTK", _stockData.numShares, address(this));
-
+        HouseToken _houseToken = new HouseToken(
+            _label.name,
+            "HTK",
+            _stockData.numShares,
+            address(this)
+        );
+        exists[propertiesLength] = true;
         properties[propertiesLength] = Property(
             payable(msg.sender),
             _label,
@@ -84,192 +135,170 @@ contract PropertyMarketplace {
             _houseToken
         );
         propertiesLength++;
-        
-
     }
 
-    function readProperty(uint _index) public view returns (
-        address payable,
-        PropertyLabel memory,
-        PropertyStockData memory,
-        uint, 
-        uint, 
-        Status,
-        HouseToken
-    ) {
-        return (
-            properties[_index].owner,
-            properties[_index].label, 
-            properties[_index].stockData,
-            properties[_index].bedrooms,
-            properties[_index].bathrooms,
-            properties[_index].status,
-            properties[_index].houseToken
-        );
+    /// @dev returns the data of a property
+    function readProperty(uint _index)
+        public
+        view
+        exist(_index)
+        returns (Property memory)
+    {
+        return (properties[_index]);
     }
 
-    function getPropertiesLength()
-    public
-    view
-    returns (uint){
+    function getPropertiesLength() public view returns (uint) {
         return propertiesLength;
     }
 
+    /// @dev returns the number of tokens spender has been approved for
     function getAllowance(address spender, uint _index)
-    public
-    view
-    returns (uint){
-        return properties[_index].houseToken.allowance(properties[_index].owner, spender);
+        public
+        view
+        exist(_index)
+        returns (uint)
+    {
+        return
+            properties[_index].houseToken.allowance(
+                properties[_index].owner,
+                spender
+            );
     }
 
-    function getTokenAddress(uint index)
-    public
-    view
-    returns(address){
-        return address(properties[index].houseToken);
+    /// @dev returns the number of shares of address owner
+    function getBalance(uint _index, address owner)
+        public
+        view
+        exist(_index)
+        returns (uint)
+    {
+        return properties[_index].houseToken.balanceOf(owner);
     }
 
-    function getBalance(uint index,address owner)
-    public
-    view
-    returns(uint){
-        return properties[index].houseToken.balanceOf(owner);
-    }
-    function approveSpender(address spender, uint index) public {
-        properties[index].houseToken.approve(spender, 10);
+    /// @dev approves address spender to use a specified number of tokens
+    function approveSpender(
+        address spender,
+        uint _index,
+        uint amount
+    ) external exist(_index) onlyPropertyOwner(_index) {
+        require(spender != address(0), "invalid spender");
+        require(amount <= properties[_index].houseToken.totalSupply());
+        properties[_index].houseToken.approve(spender, amount);
     }
 
     function getPropertyPricePerToken(uint _index)
-    public
-    view
-    returns(uint){
-        return properties[_index].stockData.price/properties[_index].stockData.numShares;
-
-    }
-
-    function getPropertyPrice(uint _index)
-    public
-    view
-    returns(uint){
-        return properties[_index].stockData.price;
-
-    }
-
-    function getPropertyTotalTokens(uint _index)
-    public
-    view
-    returns(uint){
-        return properties[_index].stockData.numShares;
-
-    }
-
-    function getPropertyTokensRemaining(uint _index)
-    public
-    view
-    returns(uint){
-        return properties[_index].stockData.numShares - properties[_index].stockData.sold;
-
-    }
-
-    function canBeCancelled(uint _index)
-    public
-    view
-    returns(bool)
+        public
+        view
+        exist(_index)
+        returns (uint)
     {
-        return (
-            msg.sender==properties[_index].owner ||
-            properties[_index].stockData.sold==0 ||
-            properties[_index].status!=Status.SaleCancelled 
-        );
+        return
+            properties[_index].stockData.price /
+            properties[_index].stockData.numShares;
     }
 
-    function canUpdatePrice(uint _index)
-    public
-    view
-    returns(bool)
+    /// @dev returns the number of shares available for sale
+    function getPropertyTokensRemaining(uint _index)
+        public
+        view
+        exist(_index)
+        returns (uint)
     {
-        return (
-            msg.sender==properties[_index].owner ||
-            properties[_index].stockData.sold==0 ||
-            properties[_index].status!=Status.SaleCancelled 
-        );
+        return
+            properties[_index].stockData.numShares -
+            properties[_index].stockData.sold;
     }
 
-    function canUpdateShares(uint _index)
-    public
-    view
-    returns(bool)
+    /// @dev returns a bool on if changes can be made to a property
+    function canModifyProperty(uint _index)
+        public
+        view
+        exist(_index)
+        returns (bool)
     {
-        return (
-            msg.sender==properties[_index].owner ||
-            properties[_index].stockData.sold==0 ||
-            properties[_index].status!=Status.SaleCancelled 
-        );
+        return (msg.sender == properties[_index].owner &&
+            properties[_index].stockData.sold == 0 &&
+            properties[_index].status != Status.SaleCancelled);
     }
 
-
+    /// @dev updates the property price
     function updatePropertyPrice(uint _index, uint _price)
-    public
+        public
+        exist(_index)
+        onlyPropertyOwner(_index)
+        onlySharesNotSold(_index)
+        isNotCancelled(_index)
     {
-        require(msg.sender==properties[_index].owner, "Only the property owner can cancel the sale");
-        require(properties[_index].stockData.sold==0, "The sale cannot be updated if some tokens are already issued");
-        require(properties[_index].status!=Status.SaleCancelled, "The property sale is cancelled");
+        require(_price > 0);
         properties[_index].stockData.price = _price;
     }
 
+    /// @dev cancels the sale of a property
     function cancelPropertySale(uint _index)
-    public
+        public
+        exist(_index)
+        onlyPropertyOwner(_index)
+        onlySharesNotSold(_index)
+        isNotCancelled(_index)
     {
-        require(msg.sender==properties[_index].owner, "Only the property owner can cancel the sale");
-        require(properties[_index].stockData.sold==0, "The sale cannot be cancelled if some tokens are already issued");
         properties[_index].status = Status.SaleCancelled;
     }
 
+    /// @dev updates teh number of shares allocated
     function updatePropertyShares(uint _index, uint _shares)
-    public
+        external
+        exist(_index)
+        onlyPropertyOwner(_index)
+        onlySharesNotSold(_index)
+        isNotCancelled(_index)
     {
-        require(msg.sender==properties[_index].owner, "Only the property owner can cancel the sale");
-        require(properties[_index].stockData.sold==0, "The sale cannot be updated if some tokens are already issued");
-        require(properties[_index].status!=Status.SaleCancelled, "The property sale is cancelled");
+        require(_shares > 0, "Invalid number of shares");
         properties[_index].stockData.numShares = _shares;
     }
-    
-    function buyProperty(uint _index) public payable  {
-         require(
-            properties[_index].status!=Status.SaleCancelled
-          ,
-          "This property sale is cancelled."
-        );
 
+    /// @dev buys a share from a property
+    function buyPropertyShare(uint _index)
+        external
+        payable
+        exist(_index)
+        isNotCancelled(_index)
+    {
+        require(
+            properties[_index].owner != msg.sender,
+            "You can't buy shares off your own property"
+        );
         //check if the property is already sold out
         require(
-            properties[_index].stockData.sold<properties[_index].stockData.numShares ||
-            properties[_index].status!=Status.SoldOut
-        , "All shares of this property is sold out."
+            properties[_index].stockData.sold <
+                properties[_index].stockData.numShares ||
+                properties[_index].status != Status.SoldOut,
+            "All shares of this property is sold out."
         );
 
         //transfer tokens from buyer to seller
         require(
-          IERC20Token(cUsdTokenAddress).transferFrom(
-            msg.sender,
-            properties[_index].owner,
-            properties[_index].stockData.price/properties[_index].stockData.numShares
-          ),
-          "Transfer of assets from buyer to seller failed."
+            IERC20Token(cUsdTokenAddress).transferFrom(
+                msg.sender,
+                properties[_index].owner,
+                properties[_index].stockData.price /
+                    properties[_index].stockData.numShares
+            ),
+            "Transfer of assets from buyer to seller failed."
         );
 
-        
-
         /*
         - transfer property token to buyer*/
-        require(properties[_index].houseToken.transfer(msg.sender,1 ether), 
-        "Transfer of hosue tokens from app to buyer failed");
+        require(
+            properties[_index].houseToken.transfer(msg.sender, 1 ether),
+            "Transfer of hosue tokens from app to buyer failed"
+        );
 
         properties[_index].stockData.sold++;
-        if(properties[_index].stockData.sold==properties[_index].stockData.numShares){
+        if (
+            properties[_index].stockData.sold ==
+            properties[_index].stockData.numShares
+        ) {
             properties[_index].status = Status.SoldOut;
         }
     }
-
-    
-}
\ No newline at end of file
+}