Yes, It's okay to buy used cars only if you win in buying a good used car.You can save money while buying used cars or else not.No one can guarantee that the used car will be without any problems because if there should not be any problem then the seller wouldn't have sold that car.
The things that you should do while buying a used car are:-
1.Always select a group of cars and one by one have a look on all.Take your time and go to a test drive.
2.Rusting in used cars is a common problem and examine the whole car and check whether there is rust present there or not. Always try to buy a rust free car.If possible lie beside the car and have a look to the hidden parts,under the hood,below the mattress.
3.Don't buy only by viewing the photographs go and have a visit to the car.
4.Ask the seller that the car had gone an accident or not ? If yes, then don't prefer to buy that car because it's serviced car that had gone to the mechanic many times.
5.A car with good engine is worth buying and hence take someone like your friend who has a better car knowledge or else take a mechanic.
6.Check the ignition is properly working or not because often there exist starter motor problem in used cars.
7.Check whether the car had been repainted .The painted car had always different shades in different body parts.
8.Open the hood and view the car's engine and always prefer to buy a car with a clean engine.If engine is not clean it means that the car was not regularly maintained by the previous owner.
9.Pay a reasonable amount for the car. Do the bargain by yourself or else take someone who's good at bargaining.