Thinking of buying Cat 963 A high hours

I've watched some videos of these things running, and I'm convinced I could buy this single machine to handle probably 10 different projects on my property. Anyway:

- 963 A 21z
- 16k hours
- cab
- less than 200 hours on rebuilt engine
- new exhaust pipe, turbo, hoses
- pins just turned and undercarriage 'rebuilt' ... tracks look a little tight
- described as 'excellent' condition (....)

owner has spent $12.8k over the last few years fixing it up. owner had it listed for $26k but has dropped the price significantly (says he just wants to be done with it). the guy sounded like a real nice legit guy on the phone. so if there are red flags here, I'm not seeing them. and I plan to do some reading to figure out how to check the machine over.

BUT I'm just a little uneasy about this whole category of machine being a money pit. I can handle it being thirsty. I can handle a little downtime. I'm looking to work on projects with this thing-- I don't want _it_ to be the project! is this the catch with these old crawlers? what are the chances I can get 200 worry-free hours from this thing? What besides engine and undercarriage wears with high hours? do these machines get 'loose' like excavators? Should I go down a size (953/943) and look for a newer machine and maybe spend a bit more?

Thanks!