It could be depreciation. Keep in mind the following while deducting amounts while it was for sale.
As Critter3 stated above, it must be held out for rent.
Vacant while listed for sale. If you sell property you held for rental purposes, you can deduct the ordinary and necessary expenses for managing, conserving, or maintaining the property until it is sold. If the property is not held out and available for rent while listed for sale, the expenses are not deductible rental expenses.
