What are the important things to check before buying reconditioned vehicle?
I'm pretty sure this is a duplicate, but let me still answer.
The three most important things when buying a used car are:
- The body. Should have no rust. If there's rust, run away! Fast! Even in parts where the rust is not safety critical, repairing costs a lot and it is hard to match the paint of an old car. And, if there is rust in non-safety-critical parts, there may be rust elsewhere as well.
- The engine. Should have no strange sounds (rod knock, piston slap) or lack of power. Also, if you suspect the head gasket is blown, you should walk away. A compression test could help to assess the engine is in good condition, but then again some recent cars with coil-on-plug design may require special tools to perform that. Also, if there are oil leaks, you should either walk away or try to use the leak as a negotiation tool for the price. Oil leaks are not that catastrophical, but repairing a leak can cost hundreds of dollars, or even more.
- The transmission. Check that all gears, including reverse, work properly and that there are no strange sounds. Check that synchronizers are not worn (exception: many used cars have the first gear synchronizer worn so much that you cannot engage 1st at speed -- this will happen to you too if you purchase a new car and drive long enough, so I wouldn't consider this a dealbreaker).
Apart from that, try to check for brake fluid leaks and oil leaks in the power steering system, if hydraulic. Check that the dashboard lights work (turn on after being started) and then turn off. If there's an error code, you definitely need to know what the error code is and how certainly it can be fixed. An error code is usually an inspection failure.
The brakes (handbrake, main brakes) should also work well. Check that all lights work, including the backup light and brake lights. Seats should be in an acceptable condition and all seatbelts should be installed. Check that seats and mirrors can be adjusted to your preferred driving position. If you live in a hot climate, check that A/C works, but if it's very cold (freezing) when purchasing a car, the A/C might not turn on, and that's acceptable.
In no case should you purchase a used car without a test drive. This is absolutely the most imporant thing: engine and transmission cannot be verified to be operating properly without a proper test drive.
There are quite many things to verify when buying a used car, and this only scratched the surface. My main recommendation is this: if you don't know this list already, or have trouble verifying the proper operation of the mentioned components, get somebody with knowledge of cars to verify the car with you. Where I live (Finland), used cars have absurdly high prices, so it makes sense to buy new, but I'm sure there are other markets where the pricing is not so absurd.