[bluecalm]

With any kind of gambling site your major cost will be credit cards chargebacks and other fraud.

>>Is there anything I could do at a practical level to keep the game fair? (no tools, no bots, no collusion.)

You can try catching unsophisticated cheaters. It will be expensive. There isn't anything you can do about sophisticated dedicated cheaters.

[logicallee]

Thanks, that's good to know.