Robbing houses seemed like a "big no" too. He'd probably end up shot, or worse caught by the police. He wouldn't have anything to come back to if he ended up getting sent to Juvie.
If you were caught by the police, you basically got exiled to the streets. Jim wouldn't keep anyone that would be considered a liability. If you were stupid enough to get caught in the first place, then you'd be stupid enough to get caught again. Various police reports led to an investigation and he wasn't risking his shop for any of us hot headed brats.