Yeah, I've found that my "art gallery" (sells only paintings) depends on the selling skill of the owner and his available family members who work as staff, so it's a pretty steady increase of stars all the way through. (Unless someone gains a cashier or sales badge, then it gets a little faster.)

When I played a bubbles & poker lot, the stars were near-impossible. Of course, the owner not having any friends yet because they were supposed to be a BACC founder had something to do with that. Especially because there were no skills involved and I was busy having the founder trying to dig up some funding. :)