Needs new tires, needs all new bushings, needs an alignment, needs rebalanced rims, needs balljoints, coolant, tranny/diff/ps fluid. Thats about 1500 right there, depending upon the cost of the tires. Add another grand if you dont do your own work.
Offer him 4500.
Also you should have looked at the oil, the cleaner the better.
Taking the car to a mechanic for a once over is a waste of money. Drive the car for a half hour - redline in the first three gears, make sure all gears shift smoothly, have a compression test done, check the underbody of the car for damage/rust/signs of abuse.