Not to rain on your parade... but how can there be any "guarantees" of success in any career? A career in the film industry is particularly risky and establishing yourself professionally can take years.
I wouldn't go into it if you think there may be something else you'd rather be doing -- it's not a career for dabblers.
You'll need that hunger, ambition, and love of the process & art to keep you going when things are slow and jobs are hard to find. Not to paint a bleak picture because many people do find success in the industry, but it would be foolish to say that it is a risk-free decision.
And it also depends on how you define success and "making it big". Making a middle-class living is certain possible over time.
