I've purchased quite a few guns online and I've not really been disappointed in any of them, except one that was advertised as "200 rounds through it" but it looks to me like quite a few more but what the hey.....

I always look very closely at pictures, and ask questions if I'm unsure about anything. Be wary of blurry pics or any pics that don't show any part of the gun very well. Sometimes an area missing in the pics is missing for a reason. And try to talk to the seller if you have ANY ideas or are nervous about anything.

Alternatively, deal with very reputable sellers like Joe Salter or Fugate. I've bought several guns from each and always been very satisfied, once I got past the price.