Yep, the one I almost bought was 10 years old and had done zero miles, I probably should have grabbed it, even though they are kinda fugly, which is why I was slow to make an offer.
Mine is a K100RS SE ABS1, and I've heard horror stories about what "can" go wrong, but even though I've been a member of arguably Australia's biggest BMW owners club since 1990 when I bought my K100RT, I've never met anyone who's ABS actually went bad? It's certainly never been a problem on my 3 "K's" or my other current BMW, my 1995 R1100GS.
I did have a dealer try to tell me that the ABS module on my K1100LT had gone bad when my front brakes wouldn't release. Basically I'd apply the front brake to slow down for a set of lights, and when I went to take off, the front brakes were locked on. If I left them for a minute or two (difficult in Sydney city traffic) they'd release again, and I could go. The dealer was quoting a couple of thousand bucks for a new module, so I had a bit of a think about it, and bought some new brake hoses, and life was good again.
It turned out the the OEM BMW brake lines were internally rotting and turning the calipers into one way valves, the pressure from the MC forced fluid and rubber mush into the calipers, but as there wasn't an equal pressure to force the "mud" back out, the caliper pistons would keep pressure on the discs after I released the brake.
I've had to reset the ABS a couple of times on my "K" bikes (to make the warning light go out) when the battery has been removed or gone flat, and occasionally I have to switch the R1100GS' engine off and back on if the ABS lights won't cancel when I ride off, but other than that, no issues, but I guess I've probably just been lucky. Cheers, Terry.