I’m a transfer student that applied to UTampa, Northeastern, Boston College, La Salle, and Villanova. I was accepted into La Salle and UTampa, and haven’t heard from the other three yet. The deposit for UTampa ($500 non-refundable) is due May 1st, but I won’t hear back from Northeastern or Boston College until early-to-mid June.
What do I do? 
The process would be the same as if an undergrad got into a preferred school off of a waitlist. I’d deposit at UTampa before May 1 if that is your choice thus far. If you then get into another school you prefer down the road you should 1) notify UTampa preferably in writing (email is fine) that you will not be attending and 2) deposit at the preferred school. You will lose your deposit at UTampa but it seems worth it to have a space secured.
You are not allowed to deposit to two or more schools. You probably checked the agreement box on Common Application that clearly states that you won’t deposit to multiple schools. However, there is a chance that they won’t find that out. Up to you.
@Lakeside2 There would be no risk to doing what I said in post 1 above – it is perfectly ethical and acceptable. If you inform the first school you will no be attending before you deposit to a preferred school you get into later it is fine. That is NOT considered depositing at two schools the first school would have been already informed that you will not attending. Changing your mind based on an new preferred admission 100% acceptable and allowable. It happens all the time – one common example is when a student gets in off of a waitlist to a preferred college. The only downside is losing a deposit to the first school.
Call the school involved and explain your situation. They may give you an extension- it has definitely been done before.