Adding on to my previous suggestions, I'd like you to remember to think of historical uses of dice games and other such games of chance, they're typically popular among the uneducated (read: just about every person in the standard D&D universe) and games of skill are unpopular (because they're easily tilted toward the person running the game).
Games of skill thereby become more popular among the educated class (read: very few individuals, typically bards, clerics, wizards, and perhaps adepts and diplomats) because they rely on (usually) logical thinking based "luck".
In either situation, there will occasionally be such a high roller that would come through and want to try to gamble far beyond what the player is accustomed to. Not only would you have to have the material funds on hand to deal with such an occurrence, but this should be an encounter that draws attention: play it out with your player so that he understands that it could make or break his income for several months.
A random level 15 Bard with tens of thousands of gold to waste is only as uncommon as a level 15 Bard.
Living in a world where Rogues are commonplace and law enforcement beyond cities, towns, or districts is slim, you'll have a hard time with thievery too. Some month you're going to go to collect and there will simply be nothing there. Not even accrued wealth from previous months - completely cleaned out. Even with magical protection, a medium or high level Rogue can clean out most facilities without much chance of being caught.
Psions or Wizards can similarly walk in, take what they want, and leave without chance of being caught.
This is all assuming you have something worth stealing there (any amount of wealth over 10,000GP is worth most spell materials and the time it takes to do it, although I can't see a lv15 Wizard terribly interested in funds he can create himself for cheaper).
A bored Rogue in between adventures, though, and you've got trouble on your hands.
