Among my friends, and 20- and 30-somethings as a whole, the side hustle–the gig you work in addition to your day job–is so ubiquitous that, in April, Glamour Magazine posed the rueful question: “You don’t freelance on the side… What kind of urban-dwelling Millennial are you?” Failing to participate in the trend might even lead one to a “Millennial identity crisis.”
It's actually a pretty common aspect of middle-class life and has been for some time. My Dad never worked fewer than two jobs simultaneously, one of which was always full-time, and often would work at three; my mother always had two. I've never had fewer than two, myself, save for the few years I was working on a master's degree. Heck, I'm almost sixty and work as a clergyman, carpenter, and luthier during the week. Even though all of those are part-time, I can't imagine any other way of living.
Perhaps if we had called it a "gig" or a "side-hustle", it would have been special.