If you become a self employed make up artist, the work and pay is whatever you want. You could specialise in say, weddings and proms, or tv and theatrical.
Make sure you go on a decent course, by a recognised body - some are worthless and a waste of money.
One of the best ways to become successful is through word of mouth - do a friends for a party and give her a few business cards. Build a decent portfolio, be prepapred to work for free/cheap for a while, until you have a decent enough portfolio to show your experience.
Always look clean and professional and clean your brushes and sponges between each client!!!
:-P Good luck :-)