I work full time in NY and stay and renting a room in the NY. I fly back every two weeks in FL. What address should I used the FL or NY? Do I have to file taxes as a NY resident. Can I switch to a Florida residency and declare taxes in NY? How does this residency/taxes thing work?

You spend over half your time staying in NY.. that makes you a resident of NY.

What is your LEGAL residence? Where is your driver's license?

Where do you vote?

You pay taxes where you live, where you are a resident. Otherwise you are committing fraud.

Sounds to me like you reside in NY.

For sure, he has to pay NY state taxes on the income earned in NY state.

NY city would probably consider him to be a NYC resident and would tax him for NY City income taxes.

But an argument could be made that he is a Florida resident.

However, it would probably makes NO DIFFERENCE in his tax bill to the various NY governments.