Build a Website for selling items uploaded by members

Need to build a dynamic, modern looking website that allows for people to register and purchase memberships then post pictures of items for others coming to the website to see, and email the member/converse with them. The money can go directly to their paypal account, but, I want a $5 fee paid to the website for each item that gets directed to the paypal account. There should be categories for the items. And all pics must e approved. There also needs to be a terms and conditions link.