Losses and other expenses incurred before the property was "available for rent" are just flat out not deductible. Period.
However, what was the extent of the water damage? There is a difference between a repair, and a property improvement. If restoration of the damage would classify as a property improvement, as opposed to a repair, that's treated differently.
If the damage occured "AFTER" the property was converted to a rental, that would matter too. It does not matter if it took you months to actually get a renter in their either. What matters is the date you converted it to a rental, which can not be until at least one day after you moved out of the property.
The property is considered "available for rent" on the first day a renter "could" have moved it. Doesn't matter if it took you months after that date to actually get a renter in there.
