Maintenance is the life of equipment. You are making a sizable investment here and one that could cost you a lot more money down the road. You can get an ideal of how a machine has been taken care of just by the general condition. Service records are the best. But even normal items can clue you into how well the owner has taken care of a machine. Are the tires worn out? Does the oil filter look old? Are the belts new or old & cracked? Is the oil fresh? I the coolant in the radiator clean or brown & yucky? Power steering fluid? Is the paint clean & in good shape? Are the hydraulic hoses in good shape and tied up out of the way? Is the seat falling apart from setting outside?
None of these are sure signs of neglect individually, but if you see several of these symptoms then chances are the owner did not do regular maintenance but performed what I call break down maintenance LOL In other words it got driven till something broke and they had to fix it. The tractor may be in running shape right now but how many items the owner has "let go" are getting ready to break down? I have seen this mentality often in people that trade up every 3-4 years. Why spend money on maintenance when I am getting a new one next year. Its the poor soul that buys it from him that ends up footing the bill.
When I buy a car I buy one with less than 40,000 miles. I figure that they have no had enough time to damage it too much in 40k miles LOL My current daily drive is a 2001 F150 that I bought in 2003. I have driven it for going on 16 years and 280,000 miles and have never had to repair anything outside normal maintenance (except one altornator and one could really classify that as a wear item). But I change all fluids on schedule, transmission, rear end, fuel filter, transmission fluid, coolant, brake fluid, (not just the oil). When the truck had 150K on it I had the front end rebuilt, its had 2 sets of brakes & rotors put on it, belts, shocks, and numerous other wear items....but they were done at home in my shop at my leisure. The truck only actually set me on the side of the road one time due to a alternator going out at around the 200k mark. I got a jump and drove it 40 miles on home. And the truck still does not use any oil or have any issues. I would take off cross country tomorrow without a thought. My work truck is a 2001 F250 diesel that has 360,000 miles on it. It has had some repairs but it gets used pretty rough and tows way more weight than it should sometimes LOL
The point of all this rambling is, maintenance or lack thereof is going to determine if a used machine is going to be a bargain or a headache. If the machine does not look maintained then I would run. I would rather buy a 10 year old machine that looks maintained than I would a rough looking 2 year old machine.