I have got one more tip for buyers. Require that you have at least a 72 hour inspection period where you can go to the FFL that you had the gun shipped to and look at it without picking it up. 72 hours is the least amount of time I would ask for. Many sellers are giving 7 days.
Below is a link that is a great website for selling or buying used or new guns.
http://www.gunsamerica.com/
Good luck and keep your powder dry!