You license your vehicles and pay vehicle sales tax in the state in which you have established residency. Legally, you cannot just pick a cheap state and title your vehicles there.
What establishes residency? In TX & SD, states friendly to full-time RVers and also tax-friendly, an address through a mailing service and applying for drivers licenses will suffice, if you have the INTENT to be a TX or SD resident.
Owning property does NOT convey residence, necessarily, so while you may still own a house in NC, if you have gotten LA driver's licenses, registered to vote and have a job in LA, Louisiana is going to consider you residents for tax purposes.
However, if you STILL live in NC when you buy the coach, no matter where you plan to live in the future, you will have the previous owner sign off on the title, bring it home to NC and title it and pay your taxes there. You don't have to pay the tax to Alabama, AFAIK
Life rocks when your house rolls
Senior Chief & the Cheese Queen