If you will be facing a lot of snow, you may want to have a winter car -- either FWD or AWD. The 330i will do fine for a RWD in the snow, but it is far from ideal.
Other than that, be sure to get service history on the car. If unavailable, it wouldn't hurt to have an independent mechanic look it over and replace any rubber parts (hoses, bushings, belts, etc.) that are worn. The cooling system is the weak point, so if you don't have evidence that it has been serviced recently, I would change the water pump, thermostat, fan clutch (if it opposes no resistance to spinning), etc. In general, be ready to spend $1000 to $2000 to get the car back in shape (standard used car purchase disclaimer).
Great car. I say, do it!
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