those are pretty good tractors
they did have some known/common issues, such as (but not limited to) PTO clutch brake failure, hydraulic clutch failures, I did an engine or two (failure to maintain), and all three of those can get pricey. Back in the day a pto clutch kit and an engine (with labor) was enough to almost buy a new M9540 (by itself, no loader). I'm sure the costs have risen since then, but it gives you an idea how much repairs can cost, which should give you an idea how much you "could" have to put into it while you own it. I'm not saying a new tractor is a better deal, both new and used have their plus and minus on each end.