The property is ONE HUNDRED PERCENT business use starting from the date you convert it to a rental, and ending on the date you convert it back to personal use.
Now if you use the property for any type of personal use while it is classified as a rental, then you will be asked for number of days rented, and number of days of personal use. This will change the percentage of business use "for you" and your rental deductions will be prorated accordingly.
Now, when dealing with the IRS, the general rule of thumb is, 'If it was easy, you did it wrong.' 🙂
If only renting for 3 months each year, you "may" have what is classified as a short term/vacation rental. In that case, any days of the entire 365 day tax year you live in the property "will" have an impact on your allowed expenses for the period of time it is classified as a vacation rental.
Things "can" get even more complicated if your state taxes personal income.
