The job of a casting director?

i'm only going into high school next year, but i've always wanted to go into the movie industry when i get out of college... i was thinking about becoming a casting director. can someone with experience please explain to me how difficult it actually is to find a stable job in the movie industry? i'm not sure that i'd want to work job to job, instead of having one stable job with a steady income. also, how do you even start becoming a casting director/what is it like, and what should you major in? is ucla a good college for this?