I bought a number of used handguns including a 22/45 a few months ago. It was first sold in 1993, as I recall, and it's been terrific, perhaps the most accurate handgun I own. I also have a used Mak and a S&W model 15. Maybe I'm lucky, but they've all turned out to be good buys. What I look for is pitting, signs of abuse, rust or other signs of neglect. It would be good if you can fire it, but if you can't, dry-fire it.
My theory is that a name-brand handgun, like a Smith, a Ruger or a Mak, is designed and engineered to last more then the lifetime of its owner and most will if taken care of.