web designer for swap web site

We need a web site with database,uploding and credits system. The web site need to be similar to [login to view URL](but much more simple) but with the only option of to swap [login to view URL] person that want to add an object to swap need to be register ,buy credits and use those credits for post the [login to view URL] we need a system to buy credits and automaticly update the [login to view URL] more details in pvt