Though I would not recommend manipulating the odds, since that can be a bit confusing for players grinding the table, if you must do it, you should warn or somehow tell the player so they don't end up wasting a huge amount of time trying to make money after it soft-locks.
The old GTA San Andreas game had a similar way to make quick money. I think if you need to cap it, it should just have a daily amount of maximum bets. (For QoH, they could get you drunk or Sonya can distract you. It could even be a way to get into certain scenarios.)
As for the money, well, I'm pretty sure story-wise the QoH has quite a few nobles show up there, so it would make sense for Sonya to have a lot of money (though she probably won't want to give it away).
Also, one more suggestion: if Erica becomes a noble, she is able to bet more. The lore reason I would find for this is that since the QoH entertains nobles, they would take more cash from nobles in a high-risk, high-reward type thing. (I personally think a bunch of rich nobles are able and willing to bet more than the average townsperson.)
Let me know what you think ;-;