Not to pooh-pooh the previous poster...but...
I think a certain amount of "realistic expectation" has to be present when looking at buying any used vehicle...much less a 8-10 year old used vehicle that cost nearly 20 grand when new.
The sting of buying a "basket case" bike never really goes away. However, there's a difference between buying a rough bike, versus buying a bike that's going to be due for some programmed maintenance and R&R of consumables (tires, brakes, shocks, etc). All of that stuff is "forseeable" if you do the research and check the bike over (or, if you're not comfortable that you know what you're looking at, taking it to a BMW dealer and dropping the $150 it typically costs to have them do a pre-buy inspection).
I hope nobody takes this the wrong way, but buying an older, complex bike, and expecting to just throw gas and oil in it and ride...is not a realistic expectation.
I say this from the perspective of a guy who bought a retired RT-P from auction, and then brought it into solid running "daily driver condition" with my sweat and credit cards.
I also say this as a guy who's taking delivery of a new-to-me 2000 K12LT later today!
If you buy a used bike, the cash-register drawer does not slam shut once you pay for the bike. In fact, some would argue that it simply opens an even bigger cash-register drawer.
On the other hand, you could always run out and spent $22K on a brand-spanking new one, have factory warranty, and just go gas, oil, tires, farkles, and programmed services for at least the first 3 years.
God bless those people who do that...they make it possible for me to buy my used bikes years later