Thirty years. The repayment method is equal principal and interest, and the annual interest rate of the loan is 4.90%, so the monthly repayment is 2,400 yuan, and the total interest is 446 15, 94 yuan. The total repayment amount is 496,000 yuan, and it will take 30 years to repay the mortgage. The sum of the house age and the loan period must be less than or equal to 40. The age of the house refers to the year when the house was built, which is indicated on the mapping map of the real estate license.