Here is a list of firearms that are practical for self-defense and (even with inflated prices) can be purchased with ammunition, safety locks, and even extra magazines for under $600:
(Not the best self-defense gun but a very affordable, low-powered handgun that is good for training people who are new and uncomfortable with firearms)
Ruger Wrangler
22LR
$225-$325
Ruger Wrangler
22LR
$225-$325