Let me try this, correct me if I am wrong
1) How can I know whether the car i bought is a good &
reliable car?
You need to bring along a mechanic to check for any
abnormalities
2) Is there some sort of warranty after I purchase the
car?
Usually no, unless the car is still under waranty by the
distributor
3) Where should I go to look for 2nd hand
car?
Classified, sgcarmarts, second hand car dealers, etc etc
4) how do I know what is the right price?
You really need to study the market price of the model you are
interested and do bargain...