The mortgage balance exceeding the property value does not affect the reverse mortgage.  If you are still living in your property and maintaining taxes and insurance, etc., your loan is still in good standing, and any funds available in your line of credit can be advanced.  If the last surviving borrower permanently leaves the home when the balance exceeds the property value, the estate is not responsible for any difference.  The loan is non-recourse, meaning you can never owe more than the property's value.  On a Home Equity Conversion Mortgage (HECM), the mortgage insurance fund would cover any loss when the property is sold.