According to a "conservative estimate" by Forbes, Kylie Jenner has earned $800 (£600) million since starting Kylie Cosmetics in 2016. In fact, when the youngest Jenner drops a buzzy collection such as her birthday line, she can earn up to $100 (£80) million in just one day. This all makes the 20-year-old the fourth youngest American female billionaire, with Forbes estimating that she'll surpass Facebook founder Mark Zuckerberg for the title of youngest billionaire ever by 2019.