Typically, interest - only mortgages have a five to ten year period with no principal payments, followed by a 30 year period with normal payments. (valuepenguin.com)
This can increase the total cost of loan repayment once normal payments resume. (lendkey.com)
They gradually increase each year, eventually leveling off after the end of the «graduation period» to larger - than - normal payments for the remaining term of the loan. (themortgagereports.com)