Good advise provided
mike,
Both burrhead and VWsig both provided sound advise.
If you are unsure what your looking at ask the LGS guy. Get specific details about the model. Perhaps grab the Serial Number. Pay close attention to details and of the condition. With any used firearm condition is key.
If you don't trust LGS guy and don't have someone you do trust that will be with you at point of sale then you should consider taking a pass. Beware of any "to good to be true deals". Usually LGS guys know their inventory and want to get best return on their investment. They do make deals but often it is with the people they have established relationships with that gets in on those.
Please don't misconstrue my comments to be negative about LGS, they are not intended to be. But if your are looking for a good deal then you may be lead astray.
I've bought both new and used firearms for LGS, gun shows and individuals. Some have been better deals than others. If I just have to have something I will usually pay more than I should.
Colts do retain their value better than some, but that doesn't mean your should pay near "new retail" for a used firearm that is still being manufactured. Some colts are collectables as previously stated. This is where knowing the specifics about the firearm in question will help.
$900 for a used colt govt model is not a good deal unless it is special for some other reason. At least that is the case here in Texas, I can not speak to New York pricing.
Good luck to you,