My sister and her two under age children having been living with me for 1 1/2 years. She works part time and pays no household bills nor does she give me money. I have asked her on several occasions to find an apartment. How many days notice do I have to give her to move out and can I serve her by certified mail? Ocala Florida

So she does not come back at you and sue you for unlawful eviction you have to give her a three day notice and then if she doesn't leave take her to housing court, clerk of courts or district magistrate and have them formally evict her.
Florida Evictions