I have an opportunity to purchase a 99 K1200LT with about 45000 miles. Other than the obvious things that we check out on all motorcycles, are there things to look out for? Any areas of concern with these bikes?
Maintenance is very labor intensive. You'll learn that as soon as you change the air filter.
My dad is a 50+ year veteran motorcycle mechanic who has worked on just about every major brand to come down the pike. He once worked on a K1200LT and called it one of the biggest pains he ever worked on, right up there with Can-Am Spyders.
I'm not saying they're bad motorcycles. I'm saying they're a pain to work on if you do your own work, and expensive as hell if you pay the dealer to do it (because it's a time-intensive pain for them, too).
A 23-year old bike will need maintenance. Keep it in mind.
The affectionately nicknamed "Light Truck" had some exhaust issues. Known to burn oil impressively if you shut it down hot, put it on the side stand, then fired it back up shortly. Word is to park on the center stand. My wife loved the powered center stand some model years had. She wanted one of those for her GL1800.
Google BMW K1200LT issues and spend some time reading up before you pull the trigger. Good solid bikes and a lot of riders loved them back in the day. Not w/o their headaches though. A lot of final drive bearing failures on those back when they were popular.