I'm going to recommend the Yugo Tokarev M57. Any 7.62x25 Tokarev will work, but the Yugo Tok has one more round (9 instead of 8 in the magazine) and it has a much better safety. SOG has them for $229.
You can buy 1224 rounds of 7.62x25 for $120 from AIM. That is pretty much the cheapest centerfire handgun ammo out there right now, AFAIK. The 7.62x25 is a screamer that will penetrate Kevlar vests, it will do the job on hogs. You can get the pistol and 2448 rounds for your $500.
If you get a few spare barrels ($39 each from Numrich) and a 9mm barrel bushing($16.50 from Sarco) you can fire 9x19 Luger in it. Ream one of the extra barrels out so it chambers the 9x23 Winchester and you can shoot that cartridge in the pistol. The 9x23 Winchester is the ballistic equal of the .357 Magnum. You get .357 Magnum power in a smaller, more easily concealed package. You get less muzzle blast, more rounds, and less recoil than with a .357 revolver.
That is what I've done.