Marketpress Setup - Which model ?


I have set up marketpress but I have a feeling it is not setup correctly.

1) On my main site, I want people to be able to login, and add a product to the main blog for sale.

The product will then be sold on the main site.

The marketplace then gets a percentage, with the seller getting the lions share.

2) From there, if someone wants to set up their own blog they can signup to create one (using pro-sites) Then they will have their own blog and list products on it. Once again, the marketplace gets a percentage and the seller gets the lion share. Is there a problem with paypal chained payments working in this manner?

3) Down the track I am then hoping affiliate could help refer pro-site people to create a blog, and refer products for sale on the main blog.

Ozbod has a tutorial here:

The same as this:

Is this the way I am meant to set this up?