Eventually, there may be abandoned casinos everywhere as people move onto other game. A quick solution for this may be to require rent at some interval. The amount of the rent isn't important, it's the fact that the casino owner will need to log in every so often to retain the rights to their land. If they fail to pay the rent, the land should be mortgaged for some time, then eventually released back to the state. Profits will go to the original landowner.