I was working almost full time as a junior in HS. Mostly worked at least two jobs my entire career, although some of it was working at my own business (tavern, rentals, lawncare, snowplowing, etc.)
When I was in the service, I was a server at a couple different restaurants. Worked as a bartender through college and after I first started working.
Counting 2016, I will have 41 years on file with Social Security since 1976. I graduated from HS in 1977. I am 56, so that is working since 16 or so. As I recall, I started working right after I turned 16, which was a state law minimum age.
And when someone says they cannot find work, I laugh...