I already own a small side business doing laser engraving (currently making nameplates for the new office my company is building). It doesn't make a profit, but it pays for laserable materials for my other projects.
I've made a little money on the side selling BBQ. I have an absurdly large pellet smoker (I've smoked 120 lbs of pork shoulder at once, and the smoker wasn't completely full). That's a hard way to make an easy living because pulling pork is annoying...plus, I'd need a health department license to do it legally.
I could do what I currently do (forensic engineering) part-time either independently or with a competitor to my current company. I know a few guys that have left my current company and now come back for joint inspections with other companies. They say that they make almost as much doing it part time with other firms as they did with my current firm.
I'd like to work at a golf course in some capacity. I don't like people enough to be a club pro (they have to teach...or at least learn how to teach as part of the curriculum). But I could be a ranger, cart guy, shop help, etc.
My back up plan (and probable future career path) is some combination of these options.