It doesn't have to be a super expensive hobby. Plenty of old cars need some love, and you can buy them (and their replacement parts) quite inexpensively. In my experience, if you're willing to learn, break a few tools and old parts, get dirty, and persevere, you'll more than likely succeed, and your bank account won't be too broken at the end of it.

(Owner of two old german cars, one which has seen a partial engine rebuild, the other significant chassis welding. No formal training doing either.)