Compile specifications for an online trading platform

I someone that will be able to draw up a blueprint document specification for an online trading platform to be used in the development of such platform. The platform/website is designed to provide free advertising space for anyone planning to sell anything from a tv, a cellphone or even a pair of second hand shoes. The design should allow for for extensive sponsored or pay per click advertisements on the right hand side of the every page. These advertisements should be linked to the linked to category that the user is searching for or posting an advert for. The site should also allow users to subscribe to a premium membership allowing their ads to be highlighted on the left hand side of the page. Users will be allowed to search the website for all they would be looking for. All adverts are to be deleted from site and server 30 days from date of posting one.