I bought a Brother Project Runway (forget which model number, but computerized) for $75 for my DIL a few years ago--brand new in box, yard sale deal. She loves it and has made a few baby quilts.
I also bought a $20 Brother (mechanical) at a thrift store and it's dandy. I ended up with too many machines at home, so I took this one to my sister's house in KY. When I'm there, I have pulled it out to work on quilts and I made curtains for her. I'd say for classes get one that's light enough to carry and easy on your wallet.