When I retired in 2004 I lived in Pennsylvania. I moved into my motor home and lived in it full time for three years. Prior to that adventure I knew the endgame was to buy a home and live in Florida.
I contacted American Home Base, a mail forwarding company that is located in Pensacola, FL. They are familiar with and will enable you to have a legal residence almost immediately in Florida as they will provide you with both a post office box number AND physical Florida address. On our first trip to Florida in the motor home I stopped at their business address and they directed me to the The Florida Motor Vehicle Office where I got my Florida licence and plates. Back then their service was dirt-cheap $10/month, as I recall plus the actual postage for any mail I wanted forwarded. I would call them perhaps twice a month and give them an address where I wanted the mail. Check out their website and give them a call -- I expect they can/will answer all of your questions!
Florida Mail Forwarding Service ⋆ American Home Base, Inc.
Good luck and welcome (almost) to the Free State of Florida!