If this is the case, then why did you apply in the first place to the other two schools? Your scenario of giving up your seat and hoping the first choice gets through I guess kind of confuses me since applying to those other schools is also an investment and requires time and money as well for the application.
Although you may only have enough money for one deposit, I would recommend doing everything you can in your power to try and save up for at least two deposits. Money is a difficult issue, for sure, and I don't know your current situation, but by the time you're applying to these schools, there has already been a lot invested into the process .. the PCAT .. the personal statements .. the applications .. the prerequisite courses ..
It'd be a shame to gamble that because of the money issue.. It's your future, and it's not something to kind of put out there and leave to "fate." Also, some schools will give you a small percentage of your deposit back. Yes, not much, but I guess it's a tiny tiny bit of comfort??