What would a good shot count be for a second hand gun guys ?
Shot count is pretty irrelevant IMO.
Most markers generally have a breaking in time, where afterwards they can have reduced dwell etc but aside from that shot count doesn't actually matter. Assuming it has been stripped, lubed, cleaned and loved constantly then it can generally just keep shooting.
Some markers in fact (namely most DM's) actually get better with higher shot counts as long as they are maintained...
But hey, what marker are you looking at? It's easier for people with more knowledge to help you if they know what you are talking about.