Raising Rents on a new purchase

[Zac Boelkow]

Hello I am buying a duplex that has below market rents. They are currently paying $650 each side. Both tenants have been in the duplex for multiple years and would like to stay. The tenants are on month to month verbal leases. I would want to keep the tenants as they are good paying tenants. I want to raise the rents $100 each side because I don't think they'll move for an extra $100. 

My question is in the state of Florida do I have to give a rent increase warning/notice for a period of time prior to raising the rents? I am assuming that they are on month to month I can just write a formal letter that maybe gives 60 days notice to the rent increase?

Thanks