I bought a new 2005 284 in 2007. You'll find that bolts work loose easy so you'll have to keep an eye on them and tighten on a regular basis. Mine only has about 300 hours on it now, I've replaced the rad hoses and installed an inline coolant heater for those cold starts [OK now down to -35C] as the rubber on the original hoses failed. I had one length of hydralic hose blow a hole, and had to replace one hydralic pump because I was playing with the pressure relief valve and messed up. ;-) The rubber O rings in the FEL controller also seem to fail quite easily, but they are easily replaced when you need to get rid of those annoying little hyd oil leaks.
I am not very mechanical, but with the ability to search this forum and get some great directions from the regulars I've managed to fix just about everything myself....so working on your prospective purchase isn't hard either. The 284 Jinma has been a good little work horse for me, moving snow, hauling dirt and landscaping on our 160 acres. I have a rear blade, tiller, and harrow for accessories... hope this helps you in making your decision.