In Florida, you would need two proof of residential address. These can be as simple as an automobile payment booklet and mail from financial institutions.

Gather Go Get the FLORiDA Card: Your FloridaCard Checklist

Further, you can list the address of a PO Box on the above documents. To make things even more easier, the post office now allows you to use street addressing for your PO Box instead of a box number.

https://ribbs.usps.gov/index.cfm?page=mtcsa

The whole point being to allow individuals as well as corporations to setup a residence and/or place of business and to compete with UPS Store which does the same.

And what about residences that have no address or street (or mail delivery for that matter)? Even the FAA allows you to list a pictorial diagram of where you live.

Everyone is missing the basic point here- What is your intention? If your intention is to defraud, well thats not really legal. But you can reside wherever in this country you wish. Last I checked, it was not a crime to be homeless without papers. People move for all sorts of reasons, including lowering their taxes, that's not illegal.