Welcome Luke !!!
Do you know any maintenance history on the bike ?
Ask the owner if a transmission input spline lube has been done, and when .
Any gear oil leakage at the final drive ?
Not uncommon to have o-rings leak on the rear brake cam shaft, possible contaminated brake shoes if it is leaking .
With the bike on the center stand, grab the front tire (tyre) try to move it forward and towards the rear of the bike, if you can, steering head bearings need adjustment .
Pull the dust caps off of the lower fork tube, and see if there is any oil leakage there, wouldn't be surprised if the seals are seeping/leaking .
Check the tire (tyre) sidewalls for a date of manufacture, there will be a 4 digit number like : 0510, that would indicate a date of manufacture of the fifth week of 2010, old tires (tyres) are not your friend .
Does the odometer work, another common failure on these bikes .
If you find any of these problems, use them as a bargaining tool to lower the price .