A coop. They split the profits with the patrons (minus operating expenses) at the end of the year. (So they can go right back and gamble away their share.)
You could even extend this by making a rule that gamblers can only wager money they've earned through shares. So there'd be no financial harm to their external life.
The cold start problem of such an enterprise could be solved by only imposing this rule after a year, using charity, or - in the worst case - buy ins.
