₪₪₪ IRS allows deduction on a loss of a rental property sale. How long does the property have to be rented before?

I am underwater on my mortgage and want to sell. I can rent the property at a slight loss monthly. But how long do I have to rent it to qualify for the 25,000 deduction if I then sell the house at a loss?
A year lease? Six months? I can’t find anything on the IRS site.