Odds of Getting In
Considering there's a bona fide clown shortage in the world, the odds of getting work are good—but only if there's work in your area to be gotten. If you're looking to start your own business doing parties, you'll need to advertise and get the word out that you're available.
Word of mouth goes a long way in the mom circuit, so you may want to do a few birthday parties for low pay at first, or volunteer a performance at the local library or county fair to gain a local following. Hand out lots of colorful business cards attached to those balloons at the end of each show.
If you go to Clown College or get experience with a distinguished circus under your belt, you'll have a chance at better jobs and can demand higher pay. Whichever route you decide to take, just fake it 'til you make it. Then keep faking it, because you're a clown.