Interest is deductible on acquisition debt up to $1 million for loans made before 12/16/2017 and up to $750,000 for loans made after that date.
Interest on equity debt is no longer deductible -- it was eliminated in tax reform. You can only deduct interest on acquisition debt. Acquisition debt is debt used to buy, build or remodel the home. Anything else is equity debt. The exact form of the loan is irrelevant, what counts is acquisition vs equity debt.