I bought an old Univega steel hybrid for $90, outfitted it with SKS fenders and Nashbar studded tires. Works like a champ. Even the cheap vinyl seat is good: it sheds snow and rain. The fenders are almost essential to keep flying snow out of your face. Due to riding over packed snow, I had to add a suspension seatpost to keep vibration down. I've used this bike for five years straight in Iowa winters, same tires, and it has very little rust. The component that will suffer the most is the chain: lubing with chain lube and then soaking it with motor oil has worked well to keep salt and rust off. And keep the frame waxed.