If you think that 3 or 4 or 5 hundred for a gun is too much to spend on a hobby, then shooting might not be the hobby for you.
I don't mean to discourage you, but shooting is a middle of the road hobby as far as expenses go, not as cheap as say..... playing checkers at home with your cousin.... but not as expensive as travel, motorsports, photography, computers, most team sports, fishing, woodworking, horseback riding, golf, music lessons, scuba diving, etc...etc......
It'll cost you at least 30 or 40 dollars every trip to the pistol range if you're an average person in an average urban location, even if you shoot rimfire, when you factor in the cost of membership, gas money, targets, target pasters, lunch ...etc...
If you shoot centerfire,..... well it only goes up from there. There's no use crying about it, it's just the name of the game. It's alot of fun, but nothing is free. I reload and cast bullets, and buy powder in bulk, etc..etc.. because I'm a university student on a budget, but I still pay in terms of opportunity cost of the time I spend at the reloading bench instead of out working a job, or spending time doing other things.
so, the point I'm trying to make is that spending 500 on a gun, is chickenfeed, being that if you spend that much on a used firearm, you can shoot it for ten years and get the same amount of money back when you sell it. Choose your firearms based on caliber, because that's the biggest variable when it comes to cost.
I suggest either a .22 rimfire or a .38 revolver if you're concerned about cost, but at the end of the day there's really no alternative but to suck it up. If you love shooting like I do, you'll just make do, and if you hate shooting, you won't bother and then it won't cost you anything.