A few comments:
- Agree with the above that any waitlist is a long-shot. Assume you will be attending the college you have deposited with.
- You can withdraw from the school you deposited with if you get accepted to your waitlist school and want to go there. The only penalty is that you will lose the deposit. You just need to inform the school (preferably in writing so there is a record) that you will not be attending in the fall.
- IF you are accepted off a waitlist you are not obligated to attend. You can turn down an offer of admission from a waitlist for any reason you like. So if the aid is not sufficient or if after some thought you decided to stick with the school you initially deposited at that is all perfectly fine.