What is the difference between iOS Developer Program and iOS Developer Enterprise Program?
As a single person you are eligible to sell apps when enrolled in "iOS Developer Program - Individual".
For an individual developer who will be creating free and commercial iOS apps for distribution on the App Store.
If you want to enroll in the Enterprise Program, you must be company with a DUNS number.
For completeness, the Enterprise program is for companies who wish to develop their own application for use within their own business, but who will not distribute those application commercially on the App Store, in fact they are not allowed to sell on the App Store.