Heads up, workforce: This is going to make you regret getting a day job.Clearly, all the hours you've spent pursuing conventional professions may have been better employed building a fan base that really loves watching you play video games. That's what Swedish gamer Felix Kjellberg — a.k.a. PewDiePie — did, and at only 25 years-old, he raked in more than $12 million in pretax dollars last year.Kjellberg is far from the only YouTube sensation making that kind of bank. According to a recent Forbes analysis , other stars — including makeover maven Michelle Phan and dancing violinist Lindsey Stirling — are pulling in millions as well.What do most of the 15 top earners have in common? Youth, for one thing — almost all of the YouTube celebs in the Forbes list are under 30. Another is that they are self-starters who do much more than star in front of the camera. So, though it seems staggering that they're pulling in so much cash, they're also putting in some serious work behind the scenes. Read more about the stories behind the salaries over on Forbes