Looking to buy an old steel frame road bike, need advice

I'm a poor college kid who tried out his roommate's old FW Evans steel frame cycle and fell in love. I've only owned crappy unmaintained big-box "mountain bikes" since I've been a kid and never really realized how much pleasure I could get from a true road bike. It would be for commuting and recreational riding in the summer. I'm just wondering, while I traverse the world of 100-200$ used bikes, what should I be looking for? What to watch out for? Thanks!