I don't know where he is getting 90 days. In Florida if there is no lease, you may even be able to say it's a week to week tenancy and all you need is 7 days prior notice. You should begin by sending a
notice of termination of tenancy as per Florida law. This is the first step. Let him be scared by sending notice and also a demand for rent if he overstays beyond the notice period. Then try the court. If you get resistance, I'm guessing it could be just a lot of talk hoping it scares you. If he believes it, let him back it up and feel free to post his claim. Best of luck with a tough situation.
Title VI
CIVIL PRACTICE AND PROCEDURE
Chapter 83
LANDLORD AND TENANT
83.57 Termination of tenancy without specific term.
A tenancy without a specific duration, as defined in s. 83.46(2) or (3), may be terminated by either party giving written notice in the manner provided in s. 83.56(4), as follows:
(1) When the tenancy is from year to year, by giving not less than 60 days' notice prior to the end of any annual period;
(2) When the tenancy is from quarter to quarter, by giving not less than 30 days' notice prior to the end of any quarterly period;
(3) When the tenancy is from month to month, by giving not less than 15 days' notice prior to the end of any monthly period; and
(4) When the tenancy is from week to week, by giving not less than 7 days' notice prior to the end of any weekly period.