$4K, he must be crazy if that is USD. You can buy a 2006 600 for $4k. Yes, almost every used bike has been dropped or crashed at least once, most require just some new plastic's. Frame sliders are great, I crashed on the track last year at about 50 mph and the bike only needed a few hundred in parts. As for the 8000km, you'd be surprised at how little many motorcyclists actually ride. The bike is probably going to need some maintenance since it's been sitting so long. I'd dump all of the fluids including the brake fluid unless he says it's been changed in the last year. Check to see the age of the tires, if more then 3 years old they should be replaced regardless of the mileage.
Thanks and Regards,