"Well first, do not buy most of the stuff from the pro, as they abuse gear most. Having said that 85 1.2 is studio lens, may not have had hard life, so your call."
Hey, I'm a long-time pro, and I can tell you that I take better care of my gear than 95% of the amateurs I know, keep gear carefully stored in fitted cases and in moderate temperature and humidity conditions almost all the time - except, of course, when actually shooting. Even in the infrequent circumstances where I must shoot in less than good circumstances, I never abuse lenses or cameras in the "elements" and protect them from harsh environments by always being prepared to take adequate precautions. As far as dropping or knocking gear around, I have almost never done so, because I need to earn my livelihood with it and need to have it in perfect working order every time. On the extremely rare occasion when any gear of mine does get messed up (two lenses and one body in over 30 years working), I have it repaired by the best available means immediately, test it for myself, and would notify the seller if it had required repair in any subsequent sale. And, if some gear looked great but had an awful lot of use - much more than the looks would ordinarily indicate, I would also let potential buyers know that as well.
When I sell my used gear, if I say it is mint, it really is. To do or say otherwise is foolish, as it can easily be discovered if you are not being truthful. I would guess that the majority of pros are more like me than what you apparently imagine. I doubt very much that you have to worry that buying from a pro would be more risky than from an amateur, and, I think that it would likely, in fact, be a safer option than buying from most amateurs. Yes, there are some pros who beat the heck out of their gear and who are deceptive about its condition, but the same could be said about many amateurs as well. The best thing to do is to judge each case individually and know that the odds aren't against you finding gear as it is represented in a sale from a pro photographer.