I’ve had people ask me why I buy used but the fact is that most gun owners don’t shoot that many rounds. Either bc they have multiple firearms, cost of ammo nowadays, the move up buyer, etc. I haven’t had any issues purchasing this way mostly thru the old calguns site but I always check the ratings (goes against me now bc I’m new to this site).
Tool marks, rail wear (like when someone says I only have 100 rds thru when it looks like 1k), cosmetics, rack and dry fire.
At the end of the day it’s hard to really tell. I have some pistols that have a couple thousand thru the pipe and looks beat up bc of holster wear. But I have some that have 5k+ rds and they look fine. Rack it, dry fire it, if it feels good buy it. Worse case you have to get a new part or have some work done but still better than paying all the taxes/fees that drive cost up.