qualified housing interest
(3) Special rule for indebtedness incurred before July 1, 1982 The term “qualified housing interest” includes interest which is qualified residence interest (as defined in section 163(h)(3)) and is paid or accrued on indebtedness which— (A) was incurred by the taxpayer before July 1, 1982 , and (B) is secured by property which, at the time such indebtedness was incurred, was— (i) the principal residence (within the meaning of section 121) of the taxpayer, or (ii) a qualified dwelling used by the taxpayer (or any member of his family (within the meaning of section 267(c)(4) )).