The good news is you are entering a business that worships youth.
I can't address getting a job. But I can offer some advice on casting.
You need to present yourself and your project as serious and dedicated.
Have an excellent script. Have specific, set dates for the auditions.
Have specific dates for the shoot. Approach a university drama department
or local theater or acting class with your proposal. Most times the person
in charge will be glad to help you find actors who will fit the parts. But
ONLY if you are prepared. You'll be surprised how many people are willing
to help a young filmmaker.
