Grab the drive clutch and shake the sled to see if you have any movement. Inspect down the spark plug hole with a light for piston burn and coloring. Look for grease around all of the xerxes fittings. Inspect the tunnel behind the black trim plates for the cracks that are forming there. Inspect the tunnel below the toe pads for the cracks that occur there. Inspect the steering column for the cracks that form there. Inspect the engine mounts by lifting up on the front of the engine. These need replacing on a seasonal basis and should be double nutted. Note how many pulls it takes when it has not been started for a week. If more than 5 then you need to rebuild the fuel pump. Inspect the reed valves for seal. Inspect your pto side torque stop to make sure the stop has not disintegrated due to pounding or to heat, and keep that gap tight. Inspect the slide rail bolt in front of the front idler wheel as these come loose real often. Inspect the rear idlers wheels as those bearings need replacement more often than the others. Loosen the track up and see how easy or how difficult it spins. Inspect the chaincase gears for assymetrical wearing. If the sled has more than 3000 miles and the seller is the original owner and is proud that he never had to do a thing to it, you are going to have to replace every bearing on the sled, gears, repair cracked tunnels, beef up steering column, replace engine mounts, rebuild the fuel pump, replace the grommets at each end of all shocks. That is why you are not paying the same price as if it was new.