While it's important to get good training and experience, I don't think it's at all necessary to major in acting/musical theatre or get an MFA to succeed.
Hilary Swank- moved to L.A., took acting lessons, 2 Oscars
Gene Hackman- started studying in his 30s, amazing career.
Madonna- dropped out of college, came to NYC, the rest is history.
I think it's about talent, ambition, and luck- when preparation meets opportunity.
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