I agree with transam with diversifying if you're going to use general ideas. There are multiple PPD websites that are already established and the market is saturated and it won't be easy to get going right off the bat. However, if you can come up with an original idea that has yet to be done, go for it starting a single website. When you have a new idea that is not out, you can find your market and it can blow up.
That's not to say you wouldn't profit with the PPD, but it's a risk. You have far less risk if you spread your eggs out. Or, like I said, if you have an idea that isn't already out there that you think could be big, go for the gamble and risk it all on that.
Just my .02 cents, everyone has their own opinions.
