How do I offer membership pricing OR automatic commission option to users?

So I've found this tutorial ( on setting up your own "Etsy" like site, and I have a few questions.

1. Is it possible for me to set up a site whereby users could set up their own storefronts, and have the option of either paying a monthly membership, OR giving us a small percentage on each item they sell? If so, how would I do this?

2. After reading the other thread, I understand that you can't use both chained payments and global cart together. So, I was wondering, if I were to enable the global cart instead of chained payments, would I be able to then have membership levels offering access to different features?

I'm totally new to multisite, any help would be much appreciated.