98827 Game/DVD Exchange Site script

I need a simple PHP script. The main objective is to become a trade site for used/new games/dvds exchange. Visitors can register and post their used games (in exchange with other games etc) and people also can post up WANTED games. So there will be like two kind of posting available. WANTED LIST and TRADE LIST. There is no checkout system will be required but member registration is a MUST. A Feedback feature must also be implemented so people can leave feedback (good/bad/neutral) regarding the trade. Also need the categorization of the games according PLATFORM(top), GENRE OF GAME(2nd sub cats),LISTING/POST. Also need ads/banner management for the site too (optional). I have a very small budget because the website will be non profit trading site for everyone to enjoy, so scripts must be cheap or free. Please pmb if you have any questions. Thank you for looking at my project.