The statute says that if you have owned the RV for less than 6 months, and the state you purchased it in was less than 6% sales tax, then you would owe Florida the difference. If the sales tax you paid was equal to or more than 6% then you owe nothing. If owned for longer than 6 months then you owe nothing.
For ALL first time registration (with a new plate) there is a one time $225 fee plus the first year registration cost. Adding a second vehicle adds another $225 fee and so on. The annual renewal is less than $100. When purchasing a new vehicle there is no fee if you simply transfer the plate to the new vehicle.