I want to build an application for the iPhone to be used inside a customer enterprise (very small, only 5 to 10 devices). But since they will be paying the application development, I don't want to distribute that application to the world inside the App Store in iTunes. How can I distribute this app to my customer? Should I get the Enterprise level subscription from the Apple Developer Program? Since I work as a freelancer, I think I can't subscribe to that program.