Hi Jeff,
You will not regret it. K100's are special bikes.
Maybe take a look at a few more, if you have time.
In UK there are still a quite number about for sale, and are priced very reasonably. The K100 being a distinct "type" of bike, attracted some very well heeled buyers who often did not use them and paid for garage services. Result; low milage and still there sitting in garages if your lucky.
Also K owner tend to love their bikes. They will look after them, keep then running, service them at the very least. So they will often pass their cherished bike on to a person that will follow on with that regime. Even if a bike looks well used, chat with the seller and your instinct will be the best judge. A bit of a tatty fairing does NOT mean the bike underneath is a dog.
Big plus (here in UK anyway) if your thinking of the restoration route, is that every little bit of the bike is still available from BMW (correct me if I'm wrong - just my experience). A HUGE difference from Japanese bikes and spares. Every bit can be ordered, from rubbers grommets to larger bits of anything. A warehouse, somewhere, full of bits waiting for us to order. The BMW way of doing things.
45 klicks on the clock...it's nothing for a K. Only just run in!
Expect to get a 150,000k and the rest out of a well kept one.
Best of all they are far more fun to ride! The RT will chew up miles and miles all day long at 125/140 kms an hour, 2 up and fully loaded. The RS with its longer gearing on the top cog is fast enough for most people, and its a fantastic bike to really "ride" rather than just twist an go.
Best of luck,
Boris the Bike