Police trade-in pistols and revolvers are usually in good shape, and priced well. A used .38 or .357 revolver, or a .40S&W/9mm pistol can be had for less than $400 easily, and you'll have money for a shotgun, as discussed above. You can search here:
Gunbroker
I've done business with the fellow below, he carries Norinco pump shotguns, they're robust clones, cheap (but currently on backorder). I know guys who won't buy Norinco (ChiCom), but will buy Russian or Eastern Bloc surplus...well, he's also got Mosin m44's Yugo 24/47s and Enfield Mk4s, also cheap, and if you'd like a surplus battle rifle those are good buys. I own all 3, they're all fine old guns.
http://www.classicarms.us/