One
may act as a guarantor for an interest-bearing loan advanced by a
non-Jew to a Jew, structured so that there is no interest payment if
the borrower pays back to the guarantor.
One
may assume an interest-bearing loan given by a non-Jew to a Jew, but
the non-Jew must agree, for otherwise one would in fact be paying
interest to the first borrower, who would then be paying it to the
lender.
If
a non-Jew lent money on interest to a Jew and then converted, he may
still collect interest, if before his conversion he establishes it as a
new loan, in the amount of principal plus interest.
