Interpretation of the IRS rules on this can differ; and it depends on which specific document one reads too. As I see it, every day it was "available for rent" is a rental/business use day. I also note that in the TTX program, vacant periods between renters does not count against you. So if the property was available for rent for 365 days and you only rented say, 250 days with no personal use, then all expenses are allowed, including depreciation for the full year.
