Are you close enough to get the rifle in your hands that way a face to face, do a serial check on it to make sure its not hot property some gooses still flout the law but best check, or 50% deposit you get the rifle to inspect not to shoot if its no good then a full refund if its as it looks then pay the other 50%. Sometimes you do stumble across these things but as you say be cautious.....
Like my CBR 1100 XX Blackbird I recently brought 2003 build with 42300 klm on the clock thats only 2820 Klms per year for 15 years or 235 Klm's a month if it was ridden every month they are there...........though I have spent $1400 on it for tyres ($750 for 2), clutch/brake fluid & oil + filter change & plugs/air filter change as I had no service history on it I do now.