What kind of storage fee can i charge a previous tenant who left behind some of her belongings?

[John Turk]

i live in florida. i was told that i can legally charge the previous tenant a storage fee for leaving behind some of her belongings. she moved on the 31st & still has her washer & dryer at the house. the new tenant is already moved in & has cleaned. i want to charge the old tenant a storage fee for not taking it when she moved. what amount can i legally charge her?