[Donark]

What happens when someone becomes so rich and winds up buying all the businesses.

Yes, you can limit one business per account but someone can just easily buy it for friends and then get Co - Owner and do most of the work. Then they could earn enough for a third, and buy it for a third friend, and get Co - Owner for that business as well.

You could probably limit the ammount of businesses allowed to join to 1, but there's still a possibility that a group of friends will wind up owning a third or more of the businesses.