What type of independant practices could nurses have?

I know that M.D.s could have their own practices and pretty much what that entails but what type of independant practice options are open for nurses? I always thought that if I became an NP one day I could open a practice of some sort but I wouldn't know where to begin. Are there any links to a list of the options for the practices that nurses could have that anybody could hook me up with?

My interests in the medical field are in pregnancy,birth,OB GYN, and infant healthcare.

Thank you!