When I was a kid, the neighbor kid made money doing yard work. He offered people at every house asking if he could pull weeds and pick up dog poo. Eventually he made enough to buy tools which probably helped him make more. Eventually he bought a 4 wheeler to reach out to further houses with his tools. Idk if his bio dad helped with any of that though. They didn't live together but the kids dad built houses. The kid started all this before he was a teen. My parents thought he'd grow up to be some sort of entrepreneur. They remember a time when he was 3-5 at most where he was going around the neighborhood dragging a small box TV by it's cord asking people of they wanted to buy it.

Alternatively, you could walk dogs, babysit, or clean cars. Services are good. Offering services that are hard to come by are good. Hand washing a car will have better results than going to a mechanical carwash, and having it done right at their house will be convenient. Walking dogs and babysitting will bring in less income but they are less labor intensive too