The first thing is to check the fluids. Oil,water,transmission fluid,and brake fluid. Make sure they are full. If any are not, it could mean a leak. Then look under the vehicle around the engine and transmission for wet spots, that could also indicate a leak. Check the tires for condition and look at the front tires to see if the wear is even across the whole tread. Next start it. listen for any noises. Check the brake pedal, make sure it doesn't go down very far, and is solid when you push on it. When you put it in gear it should engage right away. Go back and forth to drive and reverse, listen for any noises like a clunck. That would indicate bad U joints, or loose gears in the rearend. Of course you want to check all the lights and wipers and heater. Make sure it works on defrost and heat. Check that all the gauges work including the gas gauge. Also check that all the windows work and no cracks. When you drive it notice if the steering wheel isn't loose side to side. That could indicate worn steering parts. Check to see if it goes straight down the road without pulling to the side. Also step on the brake to see if it pulls. If all looks good don't pay the price he is asking, offer him less then you want to pay, then you can go up from there. Just a side note, I would recommend you have a mechanic check it also. If he says it has new parts, ask to see the receipts.