I'd think anything cheap enough to fit in what you're treating as your annual % income budget's basically fine. You won't ruin yourself or significantly harm even a modest fortune with it. More like "don't invest any part of your principal in a restaurant, it will very probably fail, but only after you've thrown even more good money after bad and suddenly you're 20-30% less rich for no good reason".

An ice cream stand or a taco truck or whatever, those are cheap enough you can get them off the ground without touching your savings given even a "modest" (call it) $100-120K after-tax income, provided you have some patience (to save a while for the big expenses rather than pulling it straight out of investment principal) and are doing a lot of the work yourself (which is the point, if it's a hobby, I'd think). Any money it makes is strictly a bonus.