Multisite (etsy style) Marketpress Site - One network cart or per store?

I'm trying to set up an etsy type of website, where people can create their own store... now if I have a bunch of people with their own stores and I am selling all store products from my site, then what happens as a person selects products from different stores? Do they all get added into a single cart, or individual carts? What about coupons that each individual stores offer? Do they get applied only to their applicable products? Would one cart then mean only one coupon, even if there are items from several stores? And what if one store offers "10% off"? How would that work if a cart contains multiple items from multiple stores? Whew! Lots of questions! :slight_smile: