>>129120730k is a lot of miles on a thumper, but if it's been maintained, it's fine. They're also fairly easy to work on.
At that mileage, assuming there's no major component failures, bearings are going to be your biggest problem (it's what i'm dealing with now, about 30k mi too). Might be looking at a crank rebuild as well.
Like I said, spend a little on gear first if it's something you're serious about. I do suggest buying decent gear out of your bike budget before you buy the bike, so you don't do something stupid like buy a bike and ride it without gear. Remember it's not the last set of gear you're going to buy - took me about 7 years to figure out the brands/styles of gear that work for me and my riding.
Bikes, thumpers especially, do need a little more love and maintenance than twins. A bike like a DR650 won't be quite as much of a maintenance whore as a KTM race-style bike (like what I have torn down in my garage), but you also give up some power/performance for that longevity and maintenance interval.
The owners manual (usually available online from the manufacturer) is a good estimate of the maintenance you'll be putting into it.
Some stuff depends on how hard/how often you ride. I sent oil samples out for analysis, i'm good for ~25hr oil changes vs, the 10-15hr interval KTM recommends, but I also seem to blow out wheel bearings more often, so I check and replace them more than the manual recommends.
