While buying these type of vehicles before you bargain check the state of the vehicle like
1)Accident free ?
2)Panel paints (color difference)?
4)Axle sounds and under body.
5)Service history(He may have kept bills)
7)An estimate for immediate maintenance
8)A mechanic testing the car is a good idea.If you have a friend in second hand car market that will be the best.
9)Ask around or check in websites for an estimated price.
After that you bargain .
I am not saying here that additional 20-30 K you give is wrong.
That may be the price that you are paying for a well maintained vehicle.
But be clear that you are not being fooled.
There is business trick for bargaining.(Start 10 to 15% lesser than what you want to pay )
Any way at that price no one else is going to buy that car.
And you can be happy you get it at a lower price if you do wait for some more time.