Buying and selling cars

I don't deal in buying or selling cars but few of my friends are doing this business....... it is very risky business and demands for lot of things in my country.... however the main tip which will work in all coutries is that while buying car from any one following must be ensured... 1. wether all documetn pertaining to vehicle are all ok. 2. the vehicle should not be re-painted... damaged..accidented vehicles are re-painted to cover accidents... 3. the spare parts of the vehicle should easily be availabel ... such vehicle are mostly liked by the 2nd hand purchasers... 4. Vehicle registration should be of the nearest city/state/province etc... to verify the accuracy of documents.. these are few tips i know.... if these are helpful to you... i will feel satisfy