I wouldn't touch it with a barge pole, and I say that with good reason.
If you search this site you will find details of a 1200 that snapped it's drive shaft which, in turn, shattered the final drive housing. This happened at about 80mph. The rider, Nick, is lucky to be alive.
That bike came from the BMW Off Road School.
I have personally repaired that bike and the condition of it, under the skin, is horrendous.
The taper rollers in the swinging arm are both completely shot, no grease, most rollers disinergrated and the cages shattered. The fixed pivot point was siezed in to the extent that we had to drill it out, the adjustable one was cross threaded so badly I've had to get a new one and have had to dress the threads in pivot point on the bike. The torque arm was siezed at both ends and the brake caliper and pistons shot.
The bike is a disgrace.
The reason it's of importance is that BMW are now using this condition and their percieved level of maintenance as an excuse to walk away from any obligation to the rider who could have been killed. This is dispite the bike having a FULL BMW Service history, carried out in their shops and presumably at the Off Road Centre. When they found out the bike had been used off road they washed their hands of the whole thing!
Buy it at your own risk but right now I would say there are much, much better and safer options up for sale.