Firstly the property must be for income producing purposes. If not apportionment will be applicable which is based on floor area if some of the area is personal. If however, the entire purpose changes then it is apportioned on a time basis.
Once we know if we are entitled to a deduction and how much of a deduction we are entitled to it is simply a matter of when it can be claimed. Expenses may be claimed from the date the property first became available for rent. Prior to that only interest, rates and insurance are deductible.