A qualified residence is a taxpayer’s principal home and one other residence.  The homes can include a house, co-op apartment, condo, mobile home, house trailer, motor home, timeshare property or houseboat.  Taxpayers with more than two homes can choose the property they want for a second home on a year-by-year basis, but for purposes of the mortgage interest rules they can’t have more than one second home at any given point in time.  A taxpayer does not have to occupy a second home in order for it to qualify.  However, if the second home is rented, the vacation home use requirements must be met, i.e., the home qualifies as the taxpayer’s home only if it is used by the taxpayer more than the greater of: (1) 14 days, or (2) 10% of the days rented.