The problem is, if you borrow it for 30 years, the interest will be calculated according to 30 years, and the interest will be paid more each time. Although you pay in advance, the total interest payment for 20 years is still more than this. If you can pay it back in 20 years, there is naturally no need to pay interest in the next 10 year, but the interest paid in the early stage will be more.

So I still choose 20 years.

Supplement:

Average capital's repayment principle is to get the principal payable in each installment from the total loan amount/repayment cycle, and then calculate the interest on the rest. In this case, with the reduction of the principal, the interest to be repaid will also decrease month by month.

As for this waiting book, the monthly repayment in the early stage will be more and gradually reduced. If you have enough monthly supply, you must choose to wait for this book. In this case, the total interest you need to pay will be less.