Home equity lines of credit (HELOCs) that were extended during the housing boom will be resetting in upcoming months, according to mortgage and credit experts in the housing industry.

The credit lines that were issued are considered second mortgages with floating rates and flexible withdrawal terms; during the first ten years, only interest rate payments are required. Now, “resets” will begin to kick in, which ultimately means that homeowners will have to pay interest rates and principal rates on their balances after 10 years.

The “resets” could require a major increase in many homeowners’ mortgages – up to an additional $500 to $600 a month. If they cannot afford the payments, banks can demand full payments on the houses and foreclose on the properties.

More than $30 billion in HELOCs dating back to 2004 are due for resets next year, $53 billion the following year and $111 billion in 2018.

Financial companies are aware of the risky “reset” payments and are saving money for potential lack of payments. Fitch rating agency recently informed the public that 2014 could be a credit nightmare due to the borrowers that took advantage of the affordable HELOCs a decade ago.