I was at 8. Parents divorced and Mom worked 2 jobs. She stopped for dinner after fulltime day job at our place, and then was off to work for 4 hours at a dress shop just to get some extra money. I rode the bus or biked home from school and was by myself for about 2 hours til we had dinner, then again til she got home at night. She only did the 2nd job gig for about 6 months, so I was only by myself for about 2 hours after that.
I learned how to cook and be pretty independent. Things were generally safe back then. I could leave and go play with friends, but I had to call and let her know. Summers I was by myself all day, or had some kind of activity.
It was really no big deal. I was a pretty responsible kid. As I got just a little older, I started mowing yards to make $$, and I was very independent from that point on.
Greater love hath no man than this....