One is the market interest rate (generally referring to the benchmark interest rate of national debt), and the other is some interest rate indexes calculated based on the capital cost of savings institutions. Interest rate adjustment is often based on the reference interest rate and then rises to a certain extent.

There are hundreds of specific forms of adjustable rate mortgages and various names. Although the specific forms are not exactly the same, the adjustable interest rate mortgage loan has a basic feature, that is, the loan interest rate is variable, but the basis, range and conditions of the change are inconsistent.

In adjustable rate mortgages, financial institutions calculate the loan interest rate by stages, and the mortgage interest rate can be reset periodically, usually every 12 months after the initial "preferential" low interest rate expires. The new interest rate is to add a fixed percentage, or "yield", to the index interest rate that changes up and down according to market conditions.

Usually, in order to attract customers, the initial interest rate of this kind of loan can be lower than that of fixed-rate mortgage, and it will be rewarded in the interest rate floating. But at first, the adjustable-rate mortgage only required the borrower to repay the interest, so that the borrower could borrow a larger amount of mortgage. When it is necessary to pay the principal or raise the loan interest rate in the future, the repayment amount of such loans will increase, which will often make the borrower unable to repay and lead to bad debts. Finally, there are so-called "ninja" loans in the market, that is, loans for those who have no income, no job and no assets.