Suppose you got a hot stock tip, borrowed agains your portfolio, and made a big profit on the new stock. You can deduct the interest on the margin loan against that income. If you pay interest in 2025 but you don;t sell the stock until 2026, you carry the interest forward and can apply it to the income then.
Your personal house doesn't produce income, there is nothing to deduct. See the instructions for form 4952 (page 3-4 of the PDF), and see the comment about personal vs investment property.
