Open-End Mortgage

There is a beginning. No end. The borrower pays off the mortgage, more or less as she wants, or as she can. The interest rates are fairly set; there's a minimum payment each month. But the duration of the mortgage is flex. It moves. Maybe it re-indexes against LIBOR every three months. Maybe there's a minimum of $10,000 in principal that has to be paid off each year.

Other than that, lots of choices. It's open.