WOW you can find a non running car in good condition for a lot less than that. Like 900-1200.
Even if its "garage kept" there is going to be rust if it was driven on the road! ITS A 30 YEAR OLD DATSUN. Check the battery tray, floor boards, dog legs, A,B pillars, under the diff, wheel wells, back hatch and spare tire. Unless he just painted it you will find some thing...... So if its not running but in the condition stated shoot for closer to 2000 for it. He is trying to get back some "lost" money in a project. (<------ slight pet peeve)