Have you heard of people going out to the stock exchange and buying shares of stock?
Have you heard about an IPO, which is an Initial Public Offering?
Both examples revolve around the public side of investing. If you’re a well established company and meet the stock exchange requirements, you can go public.
Most filmmakers do not have plans of taking film projects public. At least not yet.
What you are considering instead is raising money from a few accredited investors for a private offering.
Check out the Securities and Exchange website for more information.