The North is not really the place to look for a "good" used sled as they get so much use up here compared to down South. If you are looking at used sleds get the seller to agree to let you take it into the dealership for a going over before sealing the deal.
An alternative is to purchase used through one of the dealers in town. Probably pay a few bucks more but atleast they have most likely gone over them and may even offer some kind of warranty.