The price doesnt always dictate how a car would perform. Sometimes used cars under 1000 dollars can be as effective as brand new ones. How a car performs depends on how efficient its internal parts are.
In inspecting a car, the buyer must personally open the hood and start the car. He should have it accelerated. Sustained vibration in the engine could indicate engine mount problems. Also, the battery must be checked for excessive corrosion around the terminals on top where the cables connect. The oils should also be checked for there might be oil leaks. Of course, the buyer must also make sure the connections inside the car are firm; otherwise there are more internal problems that are unobservable.