wow, that a tough situation... i'd caution, that unless you are so strapped for money that you don't know how you're going to pay rent next month, that I'd be really careful. You NEVER want to burn your bridges if can help it. I'd simply call the school and tell them your situation. I think they'd appreciate you being honest. if you tell them right away, that gives them plenty of time to get someone else to fill your seat (which the whole point of deposits).
I'd just caution that you never know when you might need help for some reason at that school. What if you end up doing residency there or something or want to do an away rotation with them (and the list goes on), plus, the osteopathic community, medicine in general, is a fairly small community, and there's no reason to get off on the wrong foot somewhere.
But that's just IMO... take it as you want.