How Membership Works

I have D7.0.6, I'd like to offer my members the option to create their own eStore online so they can sell their own products. But, I'd like to charge them a yearly fee. Could someone explain the process. I need to make sure nobody can start uploading their products without paying a service fee. How do I do that?

Also, how do I limit the number of products for a subscribed member can upload? lets say 20 products per a member who pays for the service.

I'd appreciate your input on this. Thx.

Remove option "add to store" from standard membership level. Add new VIP or Seller membership with allowed of that action... Enter price of new membership. That all, now your site's members should buy your new membership level before sell own products