Thanks for the helpful info everyone. Just to shed a little more light though, here's some answers to a few of your questions:
I live in southern Ontario. The home I purchased desperately needs weeping tile. Instead of renting a backhoe, or hiring it to be done, I figured I'd buy a backhoe that's older, cheaper, and may need a couple things. What little money I have has been going into the renovation (the house was a foreclosure, and in very poor shape.) Then afterwards, I can use it to maintain the driveway, and dig the footings for the shop I plan on building in a few years or so.
I'd consider myself quite handy, and my time is free. I'm not a professional mechanic, but I've pulled and overhauled engines, rebuilt compressors, and fixed all sorts of other stuff. I have an acquaintance who works at a truck, coach and heavy equipment shop too. If I have to rebuild/replace a cylinder, replace hoses, or work on the injectors and pumps, and even if the machine leaks and has some slop to it, I don't mind as long as it can do what I need it to do and it's cheap.
By the way, it's being sold for only a couple hundred dollars more than scrap, and the engine was overhauled or rebuilt (not sure which) about 6 years ago. That owner was a mechanic; I don't know how long he owned it, but that leads me to believe it was probably cared for enough.