Well, let’s not gild the lily too much here. This is show business, and what it boils down to after all of the fluff and glitter are washed away is that you are going to wind up accepting the concept of sucking on a whole lot of…
… diet Cokes while waiting your turn at an open audition.

Want to know what a cattle call is like in the world of musical theatre? Watch the first 10 minutes of All That Jazz. It’s pretty much on the money.
I’m a cameraman. My son is almost 16. When he was perhaps 4, I was asked to shoot a job for a nutritional supplement drink for Pacific Rim countries. ( read: targeting an Asian market ). My kids are South Korean adoptees. I was asked to shoot some videotape of him, and his 2 1/2 year old sister. They figured they’d use the kids for background extras while I shot. The agency rep loved the boy, didn’t’ want my daughter in it at all. ( thakn god she was so young and unaware… ).
We took my son in for an audition with the adult actors playing the “mom” and “dad” in the faux Asian family comprised of mom, dad, son of 4, daughter of about 6 and baby boy of about 2. He had no agent. Hell, he’d never done anything like this before. I knew better than to shove him into this, but it was basically a day spent playing at a Discovery Zone, then eating some food and leaving.
They hired my son as “the son”. We were given very strict instructions NOT to talk to any of the other parents about who his agent was, or was not. It was a union signatory job as it turned out. I would have just said, " this is his free one"- as many folks get a S.A.G. card after three days working on a union gig legally but cardless.
As it turned out, he crashed and burned before we got to the “meal” portion of the shoot and so he started and ended his career on the same day. Sure made for some damned cute video to have and enjoy now, though.
Backstage is an excellent resource. If you want to get a taste of acting, and not sweat union auditions, contact the local fim schools. It’s April. Everybody is shooting films now, some are editing but many are shooting. You can always get your chops down and see if you like acting, by trying out for student films. Many actors pay dues by acting in them for little if any money, and you sometimes find remarkably talented folks in the casts. Go for it. 
Cartooniverse , who in Jr. High really did wear greasepaint in a production of “Pippin”… 