Final answer:
A borrower repaying interest monthly and the principal at the end of the loan term likely has a balloon loan. This loan type requires interest-only payments followed by a lump sum principal payment .
Step-by-step explanation:
Buyer A, who promises to pay off all the interest on a loan in monthly installments and to pay off the principal with the last payment, most likely signed a balloon loan agreement.
This type of loan involves making regular payments of only interest, with the entire principal amount due as a lump sum at the end of the term.
A balloon loan can be beneficial for borrowers who expect to have funds to cover the large final payment or plan to refinance prior to the maturity date of the loan.