Payment to teen influencers is often done through PayPal, which kids said is easy to hide from parents.
"A lot of people now do make money online and we don't want to have to tell our parents 'Hi, we're making money online talking to strangers,'" Alexa, a 15-year-old in New York, told the Atlantic.
For brands, it is smart business, because young influencers are often sharing the content with their peers and serve as a direct pipeline to the demographic they want to reach, according to Pitchbook. The influencer industry is growing and could be worth up to $10 billion by 2020.
It’s also cheaper to hire teens to model clothes or demonstrate products.
Instagram celebrities often charge between $50 to $30,000 for a sponsored post, Business Insider reported.
A report from Hopper called the Instagram Rich List documents how much celebrities get paid for sponsored posts.
Kylie Jenner, who has over 110 million followers, tops the list with a $1 million payout per sponsored post, according to the report.
Other top influencers include Cristiano Ronaldo, Selena Gomez, Kim Kardashian-West and Beyonce Knowles.
Atlantic reported that companies who court underage influencers often send them clothing to wear in a post. Others just send images of the items they want to be featured.
Companies are expected to spend $1.6 billion on Instagram advertising in 2018 and that could grow to $5 billion over the next few years, according to MediaKix.
Brittany Hennessey, senior director of influencer strategy for Hearst Digital Media told Business Insider that working with influencers online "almost guarantees" profit, more so than traditional print and television advertisements.
"A $100,000 (budget) doesn't buy you that guarantee on TV, on print, it doesn't buy you that anywhere. And so there are some girls who have proven that they can move product and that's what you're spending the money on," Hennessy said. "And if you're a brand, there's no amount of advertising you can do in traditional media that can guarantee [sales] like that."