Q. If a property is purchased & leases it to pay off a mortgage is the rental money subject to masser if there is no profit left over after expenses such as taxes, interest & paying off the loan?
What if the mortgage is part of a business transaction (with a heter iske) with another yid? How does the borrower and the lender calculate masser?
A. When paying off a mortgage the principal part of the payments, as opposed to the interest, is income as you are paying off the loan, and therefore subject to Maaser.
When borrowing using a Heter Isko, the same applies for the borrower. The lender pays Maaser from the interest (permitted by the Isko agreement) he is collecting.
Rabbi a. Bartfeld as revised by Horav Shlomo Miller Shlit"a