Does he do any sports or similar? My husband taught private lessons through his teens for martial arts, and always had way more cash on hand than the rest of us, haha.
I did quite a few side hustles, but only kept the money from babysitting/nannying. Everything else was donated, which probably helped with business haha.
-Collected cans and bottles. (Especially useful after Game Days and Holidays. I'd go around, bring bags. A couple times people were so hungover I just went in and gathered all the cans myself. Made good money this way).
-Dog walked, dog care (at their house, never at ours. I didn't stay nights with the dogs, but I would go over right before bedtime and let them out and go over again first thing the next morning). Also did some training for teaches dogs to walk on leash appropriately.
-Baby sat, nanny work.
-Mowed lawns, raked leaves, tilled soil in spring for gardens, spread bark, etc.
-I also picked fruit for people and took a portion of the fruit as my payment.