Hello Erik,
Yes, you can deduct mortgage interest that you pay on a home equity line of credit up to a loan of $100,000 in principal. However, at the same time, you would have to report the interest income you are receiving on the loan that you will be making, as this is taxable income to you.
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Thank you Erik and let me know if you have more questions.
Accountant
25+ years tax consulting. Specializing in returns for US citizens living abroad