eBay API and customer Advertisgin products for sale

We would like to develop a website where we have ebay products using API (only specific categories). to advertise products listed on eBay as well as Google AdSense advertising and some private customer advertising. we also would like to accommodate for individuals wanting to advertise their own products for a fee. advertised products will be listed on top of eBay product (higher ranking). customers advertising their products will have the ability to add product description and images as well as asking price and if negotiable or not with contact details (optional) and contact form to contact by email (have to have some spam prevention mechanism). need an admin interface to set categories, subcategories and fees, and manage users as well as product details options (for example a drop down of options, this should be dynamic and we should be able to add as many options as we please) should have simple user authentication and registration. Front end should look professional and search Engine friendly, use of search engine friendly URLs is a must as well as product name in browser title. Front end should accommodate for as many advertisement spaces as possible. Product listing should also have AdSense and private customer's ads (for example 5 ebay products, 1 Google AdSense space). Paypal payments as well as ANZ eGate. these are headlines, i guess you can read between the lines. Only experienced developers please.