All about the 'side hustle': How to make extra cash outside your day job

— -- A growing number of everyday entrepreneurs are taking their hobbies and turning them into an extra source of income in a practice that has become known as the side hustle.

“What I am talking about is creating an income by generating a project without quitting your day job," Chris Guillebeau, author of "Side Hustle: From Idea to Income in 27 Days" told ABC News.

Guillebeau adds that the side hustle is different from taking on a typical second job in that the idea is to turn your passions into a source of income.

The new trend, partly fueled by the internet, is also bringing in big bucks for some.

"My side hustle is running hiking tours in the city of San Francisco," Alexandra Kennin told ABC News. "I'm earning about $50,000 a year just from the side hustle."

Alicia Ostarello and Angie Sommer said that their side hustle is to write wedding vows and speeches for others through their business "Vow Muse." When not writing vows, Ostarello works as a copywriter for a tech firm and Sommer as a structural engineer. The pair said they each earn about gross $15,000 a year from their side hustles.

Tech giant Airbnb, known for its room-rental services, is also helping promote side hustles, after recently adding an "experiences" option in 40 different cities where people can sign up to sell walking tours, catered meals, painting classes or anything else you may have to offer.

Kennin said she does her side hustle in part to stay balanced, as her day job as a marketing manager keeps her mostly indoors and tied to her desk.

"I had sat at a desk for 10, 12 years in corporate environments and I realized I had moved all the way to San Francisco from Philadelphia and I didn't know the city that well," Kennin said.

Sommer told ABC News that the key to succeeding at a side hustle is that you have to be passionate about the extra work.

"You have to like it," Sommer said. "That's the hard part. You're tired, you have other things going and you still have to, like, have the energy and have the desire to do something else."

Guillbeau recommends taking it slowly at first, "I am telling people to look at what they have, the skills they have, invest a small amount of time and let's see how that goes."

Kenning, however, said she just encourages people to get started however they can.

"My advice for people who want to start a side hustle is just to get out there and do it," she told ABC News.