55K is barely broke in for the RC51. If you can get history of oil changes (you will be able to tell by the color of the site glass, they get cloud and dingy the oil stays in too long from acid etching)
Pull the fairing and take a look see.
1) Engine oil color, smell, condition.
2) Wiring- Is it butchered or spliced? This is one of the most difficult parts of owning any machine once the electrical gremlins start. (Ask Subsailor...he has a killer story, but it made him a better electrician
3) Steering head bearings....too much play? If you see little metalic pieces with a flash light or on your finger near the steering head, you may want to stay away.
4) Coolant system- like my bike I just bought back in October (This is my 2nd RC) the previous owner thought the coolant had a life time warranty on it.
NO. Again, smell, texture, any chunks of "floaties" in it or stains in the engine bay.
5) Clutch- Does it slip? Lever engage/disengage smooth?? Fluid color/consistency??? (If its peanut butter, stay away)
6) Brake system- same as clutch system for the fluid. Rotor wear (55,000 is past where I would change out for new...) and misalignments etc...
Every bike at some point in its life will get dropped. Its just the degree of the dropping force.
Don't let a driveway drop deter you from buying. I bought mine even though the previous owner lied to me and stated it hadn't been dropped. (Scratch on the pipe, mirror, turn signals marred up...no denying what happened there.)
These are a good start to your inspection....happy hunting.