Looking for a good shop system

[derfelix]

What I want:
each user can have his own shop. visible in his profile (or link from profile)
depending on usergroup he can sell 5, 10 or 20 items (as example)
the items are posted (with picture) in categories..

on a central shop page.. ALL items of all users are displayed (in categories)

if a customer clicks on the item.. he is redirected to the users shop..

each shop owner can have his own payment and delivery conditions.. one will accept paypal.. some other checks only.. its up to them..

is there a hack out there?
is there an addon?
is someone working or planning something like that?

thx for any suggestions

Felix