I don't know of any bikes that require you to remove the motor to check valve clearances. That alone would be reason not to buy it.
Worst I've seen, and I have one, is the V-Twin Buell 1125s. One cylinder is easy. But to get at the second one requires loosening the motor mounts and physically rotating the motor forward.
Inline fours like the RR tend to be the easiest to check. You just remove the valve cover and you'll be able to check all of them. If they're in spec it's really not a big deal. All you're out is a valve cover gasket.
If you have to change some shims out it's a bit of a chore.
nah, you just gotta a decent amount off the top off the bike and pull the radiator forward and stuff if im remembering prior threads correctly. I haven't done a valve job myself yet because i want to get a 2nd bike before i can set the RR aside to be looked at real closely lol