Usually it's enough to have some small amount in bankroll which does not allow players to bet a lot. When your casino starts to profit and the earned money stays in bankroll, this threshold is going higher.
I see.. There have been times where I've been tempted to get into something like this, but it seems like every time someone offers to sell the code, it ends up having an exploit in it someplace. I'm currently coding my own gambling-type game, but wasn't sure what to do about the bankroll, I was considering some crowdfunding for that part, but your thoughts there seems to make a lot of sense.