If your initial visual inspection looks like it is good shape I would do three things:
1. Take it to a local service station and have them put it on a lift and inspect the suspension and under carriage for leaks, bangs and bruises.
2. Ask owner to provide service records on vehicle.
3. Check NADA - Used car prices; link below:
Used Car Prices, Used Car Values and Used Car Reviews at NADAguides.com