You can deduct mortgage interest on your main home where you live, plus one second home, up to a combined balance of $750,000. But to qualify as a mortgage, the loan must be secured by the home, so a brokerage loan doesn’t count as a deductible mortgage. And the brokerage loan interest is not deductible as investment interest because it it being used for a personal use. (Even as an investment, the interest would only be deductible against income. If the investment doesn’t produce taxable income, the interest isn’t deductible.)
So there are no tax benefits available for the interest in this loan.
