You don't have to spend a ton of money. Many of the top shows such as Breaking Bad are not that expensive, and after the pilot you can always walk away and cut your losses if it's an obvious failure. There are many stakeholders in the show to share your risk too. Every show is basically a little startup. People check out the script, say fine, and then do whatever is needed. They can own shares, they can get external funding, they can even finance it themselves (it's always sunny in philadelphia).