Summarize this article in one sentence.
Inspecting the car on even ground allows you to see if anything in the undercarriage is out of line or sagging. It also makes it easier for you to see and check the state of the tires. Engage the parking brake and turn the front wheels to the left so the vehicle is less likely to move. The car should be clean so the paint condition is visible. Look at the sides of the car from end to end for waviness that indicates a shoddy paint job. Run your finger along the edges of the joints between panels and look for roughness that could be from residue left from masking tape. Rust, scratches, and dents in the paint and body of the car don’t affect the performance of the engine, but they can affect how much you pay for the car. It should not show any sign of rust or water damage. Look for cracks, holes, and other signs of wear and tear inside of the trunk that would indicate damage.  Check that the trunk opens easily and closes securely. Some damage like rust or scrapes could just be cosmetic. But serious rust, cracks, or holes could affect the way the vehicle performs and the integrity of the trunk itself. The tires should be worn evenly and they should match. Look at the surface of the tire for feathering or uneven wearing that could indicate a bad alignment. Bad alignment can be caused by worn steering/suspension components or frame damage and will affect the vehicle’s performance. Bad alignment or tires without much tread can be a driving hazard. Look for any black spots on the exhaust system because this can indicate leaking. Take some time to inspect the frame or unibody for damage and rust.  If you do see rust, it doesn’t necessarily mean that you shouldn’t purchase the car. But it does indicate wear and tear that could affect the price that you pay. A significant amount of rust that includes small cracks or holes could put the exhaust at greater risk of giving out and needing expensive repairs. Damage such as dents or cracks in the exhaust system are major red flags. Don’t purchase a vehicle with exhaust damage unless you’re prepared to pay for repairs. Frame damage, even if it was repaired, will greatly reduce the life expectancy of a used car. Check the undercarriage and where it connects the front fenders and holds the top of the radiator. It may be welded or bolted in. Inspect the bolt heads at the top of the fenders inside the hood. A car with a damaged or repaired frame is much more likely to break down sooner than a car without a damaged frame. Look for scratch marks that could indicate that the fenders have been replaced or realigned, possibly after a collision.

Summary:
Park the car on level ground before checking it out. Look for rust spots, dents, or scratches in the paint job. Pop the trunk of the car to make sure it is still in good condition. Check the tires for wear. Inspect the exhaust system and the undercarriage for rust and damage. Avoid cars with frame damage.