Would be worth getting a mechanic/mot tester to go with you to look it over. Check the owners forums and look for common issues with the bike so it gives you an idea of what to look for. BMW as a whole build very reliable bikes and the finish is second to non. Look for the obvious, tyres, drive train, bounce the suspension front and rear, give the forks a wipe to check for leaks, check all the lights work, check engine for any noises that shouldn't be there, pay attention the the owner of he's all about knee down on a track chances are its been used hard so check for hidden crash damage and do a hpi check which will show any finance or insurance records.
From experience the S1000RR seems a very well built bike and we have seen no problems with them as of yet.
