Hello renegade... no, you need to know a
lot more than "1 thing." Otherwise you'll have much more fun just putting all of your money into a big pile, setting it on fire, and dancing around it naked.
There have been several threads about the things you need to know and do if you want to start a paysite. I'd suggest you search for them and read them if you really think that all you need to do is protect the content and open the doors.
Here is one thread to start you down the right path.
Don't mean to be a buzzkill, but if it was that easy, everyone really would be doing it.