@Kashif: Well it is very much difficult for me to explain as what to look before purchasing any car as what I guess that depends on the preferences/ priorities of the purchaser.
but for me
I won't go for a car which has rust - that would be my first priority.
2. I will definately check for the specific model and condition price in the market before finalyzing the deal.
3. will have the car examined by a good denter to make sure it has no any major accident.
4. general condition of the car i.e. body, wiring, exterior, interior, boot (if it has any rust), engine, suspension condition, gear and for any extra work.
5. finally will check that how much do I have to spent on repair of the car and will calculate the same with the market price to come to any conclusion.
experts would also include few more points in it.
My suggestion for you is that never finalyze a deal untill you have checked the market and the car condition throughly.
do share your market search for your ride.