Here's a great collection of simple advice when starting a photography business. Be sure to go through the entire list and see if there's anything you can take back and apply to your own startup. Here's my favourite excerpt from the article:
This is normal and I have bad news for you; the fear will never fully go away. It will get easier however, and you will become better at pushing through it. As time progresses you will find yourself confidently going into jobs that you used to make you petrified. But even then, a whole new set of fears will arise as you move into more advanced jobs.
Original source found here.