I applied to CS masters programs in the US, and I have recently received an offer from a top-15 institution.

The program is unfunded, and I want to wait for decisions from other programs I applied to, some of which are funded.

However, the institution is telling me that they are only giving me one week to make my decision (I must respond by 3/13) and that I must deposit $5000 in order to secure my admission. As the school is not giving out a funded offer, they need not abide by the April 15th resolution.

Seems somewhat unethical to me, but in any case, I have some questions:

a) How common is this? For MS programs to force you to deposit huge sums of money within one week of the decision?

b) If I accept this offer, would it somehow notify other schools that I have accepted this offer, and make other schools less likely to give me an offer?

c) Let's say I decide to shell out my 5k -- would it be unethical for me to withdraw at a later date if I get into another school? They're not investing anything into me, and they get free money.

d) If I go the route of c), with whom would I be burning bridges with? Only the admissions folk?