Most of the movie producers start investing in the movie industry after they have already made a lot of money from other businesses, or have inherited the money. Meaning they have enough money to invest in such a risky business. Also, I suppose they could take out some sort of loan if they needed to, and pay it back later when they get all the money from their movie. However, that is very risky, because you never know if the movie is going to succeed or not.
Here is an article on how a Hollywood movie gets made and why it costs so much money, if you are interested...I seen some of your previous questions and you seem to be interested in the movie making industry - http://funadvice.com/r/14pstlmm144
I think that if the movie makes a lot of mone, meaning by people going to see it and buying the DvD once is out and stuff like that. I know at first it does not seem like a lot, but when you have this going on all over the U.S. and sometimes all over the world, it is tons and tons of money.
They all start small and work their way high. There are tons of grants and loans you can get in the arts field to get you started, if you're interested. Once small jobs rake in some cash, thats when you move on to bigger things.
Just an idea.. if you read some bio's of successful guys in the industry, you'll get an idea on how they each started. :)
i know one director had to take out a loan from the bank and he also had to use some from his own pocket
from thier last movie if success,