Don't apologize, it's a good question. If they aren't used to having a lot of students then you might need a co-signer. The places I live are used to students and I just give them a copy of my financial aid budget/award showing that I will have a specific amount of money to live off of (unless mom and dad are paying)--that may be between 15-20K depending on where you go to school and the cost of living. That should work or if all else fails ask the leasing staff.
a co-signer is someone that will be held financially responsible should you be unable to pay your rent...it can be your roommate depending on their finances, but usually it's a parent or relative or someone with good credit that's willing to vouch for you.