Odds of Getting In
If you have a good grasp of math, a mind for games, and are at least passingly personable, your odds are pretty good as long as you put in the requisite time and effort to hone your skills.
It also helps to be in the right place. If you're in Vegas or Atlantic City, or gambler-friendly states like California and Louisiana, you'll have a better chance than you will in a state like Utah where all gambling is completely banned (source). No one's going to hire you if they can't legally operate in the first place.