That's normal practice, yes, but the contract should tell you the specifics - if you go to accept the offer there should be a website with the full legal terms you have to agree to before you accept, and that should spell out the exact policy. (if it somehow doesn't, contact the admissions office)

Do most schools have a grace period? I’m seeing it in some of our offers and not in others. For example, pay non refundable deposit by next week. But you can revoke acceptance by May (or whatever) and you aren’t on the hook for the entire next year’s tuition.