setting up a buddypress store similar to etsy

Hi,
How do i customize my store to sell books or products on a commission base from buddy press users?

1) Users can create their own books (buddypress is installed)
2) Users upload their book information
3) Users set the price for their book
4) Book gets approved and into the marketplace
5) User browses - they buy a book and get a download link when they buy the book
6) My site (bibliocrunch.com) takes 15% commission from each book sale and

Any info would be helpful!

Miral