Out here on the west coast, that rig would go all day on Craighslist for $8,500173k on a 5.3L? Engine is barely broken in. Keep up with oilo changes and that engine will go 300K+ no problem. Look through receipts. I suspect the fuel pump has been replaced and the tranny likely rebuilt in the last 50k. If it has then that is a huge plus. Look for receipt on transfer case rebuild or atleast the rear case half replaced if it was needed and the anti pump rub plate installed. Also the front suspension was likely rebuilt (Tie rods, ball joints, pitman and idler arm, control arm bushings) these are all huge plusses if already done. Now the 4k is a little steep for a 20yr old tahoe BUT if certain combinations of the things ive listed have been done then 4k might not be such a bad deal. I still would work him down to 2-3k if possible.