What Is A Flexible Mortgage? A flexible mortgage is a secured loan, which can be paid back in differing amounts while providing access to the housing equity (within pre-agreed limits).There are five key features with a flexible mortgage: the ability to pay the mortgage off early through overpayments or lump sum payments, the ability to borrow money back by withdrawing lump sums, making underpayments, and having payment...... Similar Editorial : Flexible Led Lighting by Matthew Storie. | Source : Mortgage Broker Web Site