When you were a kid they called it 'moonlighting.' Now a part-time job is known as a 'side hustle' and 37% of Americans have one.
Bankrate.com's Amanda Dixon says most side hustles are in just a few categories.
"Home repair and landscaping, babysitting or childcare, online sales and crafts."
Dixon says a certain kind of American is most likely to moonlight.
"Millennials are more likely than any other age group to say that they have a side gig, men are a bit more likely than women to earn extra money on the side and republicans are a bit more likely than democrats to have a side hustle."
Dixon says men usually make more than women -- typically because what they do pays more.
Dixon says it's a trend that will continue to grow.
"There's definitely proof in research showing that the gig economy is growing; more and more people are turning to freelance work and part-time jobs and I think that it gives people freedom and flexibility that a 9 to5 just doesn't give them."
Dixon says the average side hustler earns nearly $700 each month.