Make sure the frame/fairings not cracked.
Check rims and discs if its even and not out of shape.
Check Tyres if its treads are new, try not to accept old and worn
out tyres.
Check ur insurance company (NTUC etc) the exact price for your
insurance premium, so that bike shop cannot chop u on the
price.
Make very sure and discuss the $$ matters with the boss. The
interest percentage, downpay, full sum, etc etc, check properly
what u paying for. *very important*
Check meter, lights, furl guage, everything on the meter area if
its working.
If bike has a hard time starting, request for new battery. If it
keeps can't start, don buy coz might be problematic.