Bava Metzia 72 - Guarantor and Loan Assumption

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.