New (to me) info direct from FAA Registration Branch: A new or used drone which has never been registered under 14CFR Part 47 (which applies to all aircraft) cannot be flown under a Section 333 Exemption (commercially) until an N number has been granted and affixed to the aircraft. The carbon copy (pink slip) can only be used when applying for a new registration for an already registered aircraft. My understanding is that as of Feb 19th 2016 you'll need a hobby/recreation registration number in order to fly the drone for training, etc., which will be replaced by your N number when granted. So if you have the drone you intend to use under a 333 you've applied for, you can use your personal registration number temporarily and start the Part 47 registration process any time. You'll need the 333 and a registered aircraft in order to legally charge for your services. These are separate issues handled by separate FAA branches. Registration Branch is a little swamped right now with all the new hobby/rec questions, but they'll eventually catch up!