Online Broker Website and Back End System

I need an e-commerce site with content management to allow online users to post items for sale (Cars, Boats, Jewellery, etc...) The site should allow the potential buyer and seller to exchange messages privately regarding the item for sale. The items should be posted with the following information: Item Name Item Description Category eg. Auto, Boat, Jewellery, Furniture Sub Category eg. Car, Minivan, Truck etc Pictures Videos Post Date Expiry Date Price Buyer Protection (Yes or No) If there are open negotiations the status of the item should be "in negotiation" The seller of the item can negotiate with more than one buyer at a time, and the system should show how many negotiations are in progress. Once the seller agrees to buy the item the status should change to one of the following: Sold In Evaluation An item that is not in negotiation or evaluation should have the status "Available" Items that have expired should give the seller the option to renew for a further period or delete the item. If the item has buyer protection this indicates that the seller is willing to offer an evaluation period of time where the buyer can cancel the sale after taking posession fo the item should any defects or problems arise that were not disclosed to the buyer. During the evaluation period the website will hold the buyers funds in an escrow account and will release the funds once the buyer has accepted the item or the trial period has elapsed. The trial period begins when the sale item has been delivered and the funds have been deposited. The site should generate the following documents (I will provide the templates for these): 1. Sales agreement including the evaluation period if it is chosen. 2. Acceptance confirmation if the sale is accepted after an evaluation period. 3. Rejection of sale during evaluation period. The site should have all the functions of an online sales site, and allow users to create personal accounts and manage their for sale items. Buyers will also have to create an account in order to negotiate/purchase/evaluate an item. Buyers can deal with multiple items at once and are able to see the statur of their evaluations and funds in escrow by logging in. The Website will earn a comission (flat or percentage) on all sales. The Website should also allow banner ads to be sold. Sale items should be broken down by category and dynamic links to each category should be available on the main page. Browsers should be able to do free text searches on the sales items as well. The Administrator should be able to create new categories and sub categories of items. This is the main idea I can provide more detail when requested.