This is a profession that's changing all the time as we move further into the digital age. The makeup artists we're talking about here aren't the ones who'll tend to your hair or cosmetics at your local beauty salon; they're the sort who'll be invited to apply makeup for television or film productions, and may be paid to create or promote makeup brands for manufacturers.
Social media is having an increasingly large say in who makes it within this profession. Instagram and YouTube are full of makeup artists demonstrating their skills in pictures and in video. If they develop a large enough following, big brands will pay them for endorsements. The larger your social media presence, the higher a fee you can demand. Obviously, it helps if you're also good at applying makeup and have a flair for design, and a cosmetology license doesn't hurt either!