Unless you're a "classic and vintage" sort of guy, I'd keep looking too. $300 for a 30 year old bike is just plain too much, IMHO. Unless you're looking for wall art. And bikes don't get better (or more expensive) with age like wine or scotch.

Sounds to me like you're looking for cheap transportation, not wall art, and not "classic and vintage".

Remember too to leave enough leftover in the budget for a good lock. Not a cheap lock, but a good lock. College campuses are hotspots for thieves. $40-$50 gets you in the neighborhood.

You'll need a tire pump for at home, and spare tubes too. And some basic tools to change the tire.

Pretty soon your $400 bike budget becomes a $200 bike, and $200 accessories and spare parts budget.

EDIT: Don't despair. It can be done, BTW. I started out with a $500 budget for the whole kit and kaboodle. That got me into the low end of new LBS bikes. The bike was $370, and with a helmet, lock, some spares, tools, and tax, it came in at just over $500. I put just shy of 3,000 miles on that bike before I'd saved enough for its replacement--a $100 fixer-upper craigslist special that I fixed up and rode for the next seven years.