Just an honest opinion for a used car that is worth buying... First of all, it must be very well maintained. Careful inspection of the car prior to buying is necessary. The engine should have undergone regular tune up/change oil prior to your purchase. All of the electronic and electrical systems, including lights, wipers, power windows and locks, sound setup, and air conditioning, must all be functioning. The car's body should not show any sign of rust, such as bubbles on the paint (especially on the roof). Doing a repaint or replacing the whole part is costly. Although, for me, few light scratches on an old car may be acceptable. Check also the condition of the tires and brakes. One more thing, an abused car that was not given proper TLC has a moldy odor inside and could have a bad suspension system. Be wary of a car's low asking price, it might indicate more repairs and high maintenance costs on your part. 'Hope this would help...
Check also for radiator and engine leaks. Moist areas, especially with thick black grease, over and under the engine would indicate leaks. This may also be costly. An extra budget must be readied for unexpected repairs and part replacements if you are really decided to buy a secondhand car...Happy driving!