“A Millennial’s Field Guide to Mastering Your Career” Advises Young Professionals to “Always Have a Side Hustle.”

“A Millennial’s Field Guide to Mastering Your Career” advises young professionals to “always have a side hustle.” However, for many Millennials, a “side hustle” is not necessarily optional (almost half of freelance workers are between 18 and 34), probably because the median income for full-time workers ages 18 to 34 has fallen more than $3,000 since 200…