We could go on for hours about the things that could be worn out on a 4000 hour combine, but then on the other hand if it was inspected every year and the things that were wore replaced the combine could still have some decent life left in it. If it was poorly maintained then you could be looking at repairs numbering in the tens of thousands of dollars to get it up to reliable working order. If you could get a dealer to inspect it and tell you what they find that would be a start, it looks nice form the picture, but if it needs all new chains, belts, shaker bushings, augers, rotor rebuilt, new cone, concaves, dry rotted hoses, all fluids changed, etc, etc, you could be looking at over 20k or better to get it in shape. Also if you can check the grain tank out for rotted metal where the cross augers meet the vertical auger, you could spend alot of money and time there if work needs to be done. I'm not trying to scare you from a 4000 hour machine but before you buy one with that many hours get it inspected and see what it needs, I learned a lesson one time by buying a combine that I never went and saw first. I got it home and had a project on my hands that winter. I had a 1987 1680 that I ran a 25' head on and I felt it fit that machine just rite, I cut wheat and soybeans with it. Good luck with your search