[filoleg]

It depends entirely on school.

Mine wasn't like that (and still isn't). Multiple friends of mine are graduating from NYU this month, and their situation isn't like like that either.

Every school I've ever encountered gives an option to purchase (with some being way more affordable than others). E.g., NYU JD (law school) cap and gown is roughly $98 to purchase (not to rent) this year.