If you can get it for next to nothing, I suggest you do. If it runs and moves metal, it's worth it.
Spare parts are doubtful, very few antique hammers have even semi-readily available parts. On the flip side, these old helve hammers, and most old mechanicals are simple, and easy to fab replacement parts for.
If you're not willing to do that though, your only real option is to buy a newer utility type hammer, which often has off-the-shelf replacement parts.
Still, if it's really that cheap, run it till the wheels fall off and it'll pay for itself, then pass it on to someone who's willing and able to repair if you're not.