Look at page A3 of the 1040 instructions. "Interest you paid" Lines 10 and 11. Home Mogtgage Interest. . "A home may be a house, condominium, cooperative, mobile home, boat, or similar property. It must provide basic living accomodations including sleeping space, toilet, and cooking facilities. " According to this, even a Coleman pop-up would qualify. This information applies to "your main home or second home".