I think you need to take them on a case by case basis. I prefer to look at the actual gun Im buying before I buy it, as "shooting" isnt the only issue. A lot of those guns were poorly maintained and/or stored.
I recently bought a NYS Department of Corrections 2" S&W Model 10 for $325. I had the pick of three, and chose the one that seemed the best mechanically. The one with the best overall finish, had some issue with the cylinder, and it didnt want to spin freely, nor open smoothly. Felt like something was off when you pulled the trigger as well. The other one I passed on looked like it had been skipped of the concrete more than a few times.
Mine seemed to be the winner, until I was cleaning it after shooting it a couple of times, when the barrel came loose while cleaning it. Seemed fine while I was shooting it, and even while I was cleaning it, just rotated off when I was wiping it down at the end.
My first thought was the frame cracked, but I cant see the hint of any anywhere. There appears to be a hardened glob of thread locker of some sort at the shoulder where it times up. I left it alone, and put some LocTite on the threads and timed it back up. Ive shot it a couple of times since, and it seems fine. Maybe S&W shouldnt have stopped pinning the barrels.
I also had a couple of SIG P6 trade ins, One looked brand new, with barely a wear mark on the barrel, the other, showed a lot of wear, inside and out, and the barrel had a "smiley" that was worn into the barrel, and looked a lot worse than my one Glock, that has a documented 135,000+ rounds through it. Looks like it wasnt one of the usual "carried a lot and shot little". Maybe it was one of the range guns and everybody had a go with it.
I still think your best bet is to have an idea as to what to look for in what youre looking at, and go over it closely, in person, before you buy. Even then, youre still taking your chances. Ive bought a lot of used handguns over the years, and for the most part, havent had any problems doing so. Got some real good deals, and real good shooters too. I guess youre always still going to have the odds to deal with though, new or used.