This calculator computes the payment amount necessary for a mortgage with a balloon payment, using monthly interest compounding and monthly payments. A balloon mortgage is a type of home loan in which the borrower makes small or no payments for the early years of a mortgage, typically five to seven years.When I buy existing seller financed loans, I underwrite as though the loan will fully amortize. Learn everything you need to know about balloon notes in mortgage loans. Find out how they work and how they can affect your finances. A balloon mortgage is a mediumterm real estate loan that allows borrowers to make low or no monthly payments. A balloon payment is a large payment due at the end of a mortgage.