There is a story requirement; you have to be a little ways into chapter 1 (once you get through the maid academy, you should be far enough). I may remove this stipulation, I wanted to prevent players from getting into debt within the first hour or so of play and getting stuck in a debt loop without enough ways to make money, but maybe halfway into chapter 1 is too far into the game.
I'm not sure about the perfect timing - I'm a programmer, not a game designer. It's kind of hard to get into debt anyway if you don't try very hard to do so on purpose. I mean, a few minutes of working the streets, combined with the traits you earn doing so, and your money won't ever drop below a thousand or so. I think to get into the debtor's prison the ordinary way is not easy to achieve after the first minutes of playing, and the bandit camp can only be reached far later. But on the other hand, it's okay not to put each and every possibility into easy reach all the time.