I agree with the many that have said 2K is to much. I agree with the many that have said the rust is to wide spread to be cost effective to repair. I wouldnt buy that car but as I read all the posts you kept coming back and giving reasons why you want to buy this car so it appears that your mind is really already made up to buy the car. A few things to consider, does your state have a yearly inspection. If so I would only buy the car after it passes an inspection. Offer to pay for the inspection before you buy it, if it passes theres no issue, but if it doesnt you havent lost the 2k. Its one way to make sure the underbody/frame is safe. Its really hard to believe that a car that has sat outside in the elements and rusted as bad as this car has, that the underbody/frame wont have the same type of rust issues.
Another thing that would seem to be a problem is that you say the car is for your friend and not you. Both names will be on the title and insurance? Again that is most times the best way to end a friendship. It all sounds good but once the car starts to need money thrown at it one preson ends up paying while the other doesnt want to put more in it or doesnt have money to invest. Just a bad situation most times.
The last thing you say is that the owners grandson will crush the car. If that is really the case why does he want so much money for it? he will only get $400 maybe $500 bucks tops to scrap it. If you want the car wait until just before he decides that then give him $600 for it. Its really only worth that or more if you scrap it out. And then you have to find people to buy the parts which usually means storing the parts somewhere until you find buyers interested. Remember the exterior body parts are going to be worth nothing.
Best of luck and I hope you make the right decision.
Rod