I'd suggest renting as well... Invest in a good editing system... Rent based off the project's needs... I'm starting a production business as well, and that's the model I'm using... Besides... Four years ago I bought an HDR-FX1. Four years ago, and now that camera is a dinosaur. Twenty years ago how long was BetaSP good for? A lot longer! Our local news market didn't upgrade until 1998. My point is that camera technologies are rapidly evolving. If you buy something right now without much potential for making an immediate return you'll be wasting your money. (I'm preaching to myself here!) Besides, tomorrow a "better" camera will come out, and then you'll just be frustrated.
The only solid advice I have on what camera to use is to go tapeless. Depending on your camera preferences and whatever look you're going for... Go with either P2 or EX technologies. I know a lot of people don't trust tapeless because it can get deleted, but create some redundancy systems and you should be good.
But the question isn't so much what camera you should get, but really the business questions of if your idea is profitable and if you have the prospects to make it happen.
Shooting video without a plan is one thing, but running a business without a plan is another! (Again, preaching to myself!)