Tax-accounting related question:

Anne White, a client who lives in Richmond, has owned a second property in Wintergreen for three years. Each year, the taxpayer rents the property during the winter months (December through March), and uses the property for personal reasons for the entire month of July. However, for two of those three years, her daughter Ellen lived in the property for those three months, paying less than fair rental. For the remainder of the year, rentals are sporadic, usually totaling about 100 days. The taxpayer would now like to deduct interest paid on the mortgage on this property as interest on second personal residence. A colleague told you that you probably should check Code Sec. 280A(d) on vacation homes to see when (if at all) such a rental would be classified as a residence. Please write an opinion letter citing applicable primary authorities to support your opinion to Anne on CPA format.