If you are going to buy a locally used R6, then havea background check (call previous owners talk to super bike riders where it is previously used, track days .. e.t.c..,
Try to get insight if it was abused by any of the prev. owners...
once that is clear check bike in person "just like a second hand car" new clutchplates dalwana koi khatarnak baat nahi... R6 is prone to ECU malfunciton from 2005 to 2012 so if that you find replaced still koi bari baat nahi...
they are made of aluminium cast iron any accident cannot be hidden...
Check tires health, look for any un usual noise from engin once radiotor is ambient hot, notice if bike is capable to cool down it self once radiotor fan goes on... or does it continues to heat up and finally die...
ye sab lazmi or zurori checks hai...
Hope that helps.