These Friends Launched Their College Side Hustle in Just 1 Hour — Then It Hit 6 Figures a Month: 'It Was a No-Brainer' The duo had a major revelation while studying abroad — and it led to millions of dollars in sales.

It's the era of the side hustle, and if you've ever considered starting one to earn some extra cash outside of your 9-5, you're in good company. These days, more than one-third of U.S. adults have side hustles, and their supplemental gigs make an average of $891 a month, according to recent research from Bankrate. Of course, the most successful side hustlers see much higher earnings, especially when they start a business that brings in nearly as much as — or significantly more than — their full-time sources of income.

^{Image Credit: Courtesy of 437. Hyla Nayeri, left, and Adrien Bettio, right.}