Used but new enough to be nice and reliable.
Cash is best, but nothing wrong with paying some cash and financing a part of it. There's a world of difference between financing a $55K new car and financing $5-10K to supplement a cash down payment for a used car.
I have found that choosing a short finance term (24-36 months at most) is another good check on the impulse to buy more than you need. And the loan is gone soon, too. 5 and 7 year auto loans are predators' tools.
I bought my son a used Nissan Altima earlier this year, total was about $9K. It's 6 or 7 years old, but in good condition. I expect it'll last with minimal drama while he's in college, and tolerate his absentminded preoccupiedness not changing the oil ...
Last year I bought (for myself) a used 2006 M3 ... to replace the 2002 M3 I crashed
. Pristine condition, 52K miles. First owner tracked it for a couple years and then it sat in a garage. Paid about $20K for it, and the only work it needed was about $400 to replace the obnoxiously loud aftermarket exhaust with an OEM muffler I found on eBay for $200. I can't think of any car I'd rather have for under $50K. I watched autotrader for several months waiting for the right one to come up, and ended up flying out of state to buy it and drive it home.
We also have a beater 2003 Civic we paid $4K for. 140K miles. My eldest crashed it once when he had his learners permit. Completely smashed a Hyundai's front wheel under it, but somehow the Civic survived with a slightly bent bumper. Got a can of paint and a new plastic bumper offf Amazon, good as new, er, 2003.
You can get basic and reliable for $10K, or fun for $20K, if you look and aren't in a rush.