my first bike was a 1998 ninja zx6r. Because it was my first i wasn't paying much attention to all the cosemtics of the bike but more mechanical, mind you, the owner that had it from new took good care of it, but replaced the motor because of high km's, the motor was starting to get "tired". i saw the replaced motor that was sitting in the owner's garage, and everything checked out, he even had the paper work from the motor swap,
I've long sold that bike just because it was getting older as i rode it, so i decided to get a new bike. I now switched to a 2006 kawasaki ninja zx636 special edition. This time though i made sure to check everything on the bike from chain, to fuel leaks, oil leaks etc. The bike i purchased only has 3000KM on it so i expected to find absolutely nothing wrong with it, and i didn't it was completely clean, the owner of the bike allowed me to remove the fairings to check out the motor and electrical behind all the hidden plastics, which was really nice of him, it made me feel a little more comfortable in purchasing his bike.
The only imperfection i found on this bike was a zipper scratch on the gas tank, it sucks, but to find a special edition bike with only 3000 km on it wouldnt be easy again.
I know a lot of owners won't let you remove plastics, but thats when an experienced rider will come in handy maybe they can help you look !
Anyways sorry for going on forever haha, good luck in your quest for a bike !
safe riding !