The traditional fixed rate mortgage is the most common type of loan program, where monthly principal and interest payments never change during the life of the loan. Fixed rate mortgages are available in terms ranging from 10 to 30 years and in most cases can be paid off at any time without penalty. This type of mortgage is structured, or “amortized” so that it will be completely paid off by the end of the loan term.

Even though you have a fixed rate mortgage, your monthly payment may vary if you have an “impound account”. In addition to the monthly “principal + interest” and any mortgage insurance premium (amount charged to homebuyers who put less than 20% cash down when purchasing their home),  some lenders collect additional money each month for the prorated monthly cost of property taxes and homeowners insurance. The extra money is put in an impound account by the lender who uses it to pay the borrowers’ property taxes and homeowners insurance premium when they are due. If either the property tax or the insurance happens to change, the borrower’s monthly payment will be adjusted accordingly. However, the overall payments in a fixed rate mortgage are very stable and predictable.

Adjustable Rate Mortgages (ARM)s are loans whose interest rate can vary during the loan’s term. These loans usually have a fixed interest rate for an initial period of time and then can adjust based on current market conditions. The initial rate on an ARM is lower than on a fixed rate mortgage which allows you to afford and hence purchase a more expensive home. Adjustable rate mortgages are usually amortized over a period of 30 years with the initial rate being fixed for anywhere from 1 month to 10 years. All ARM loans have a “margin” plus an “index.” Margins on loans typically range from 1.75% to 3.5% depending on the index and the amount financed in relation to the property value. The index is the financial instrument that the ARM loan is tied to such as: 1-Year Treasury Security, LIBOR (London Interbank Offered Rate), Prime, 6-Month Certificate of Deposit (CD) and the 11th District Cost of Funds (COFI).

When the time comes for the ARM to adjust, the margin will be added to the index and typically rounded to the nearest 1/8 of one percent to arrive at the new interest rate. That rate will then be fixed for the next adjustment period. This adjustment can occur every year, but there are factors limiting how much the rates can adjust. These factors are called “caps”. Suppose you had a “3/1 ARM” with an initial cap of 2%, a lifetime cap of 6%, and initial interest rate of 6.25%. The highest rate you could have in the fourth year would be 8.25%, and the highest rate you could have during the life of the loan would be 12.25%.

A mortgage is called “Interest Only” when its monthly payment does not include the repayment of principal for a certain period of time. Interest Only loans are offered on fixed rate or adjustable rate mortgages as wells as on option ARMs. At the end of the interest only period, the loan becomes fully amortized, thus resulting in greatly increased monthly payments. The new payment will be larger than it would have been if it had been fully amortizing from the beginning. The longer the interest only period, the larger the new payment will be when the interest only period ends.

You won’t build equity during the interest-only term, but it could help you close on the home you want instead of settling for the home you can afford.

Since you’ll be qualified based on the interest-only payment and will likely refinance before the interest-only term expires anyway, it could be a way to effectively lease your dream home now and invest the principal portion of your payment elsewhere while realizing the tax advantages and appreciation that accompany homeownership.

As an example, if you borrow $250,000 at 6 percent, using a 30-year fixed-rate mortgage, your monthly payment would be $1,499. On the other hand, if you borrowed $250,000 at 6 percent, using a 30-year mortgage with a 5-year interest only payment plan, your monthly payment initially would be $1,250. This saves you $249 per month or $2,987 a year. However, when you reach year six, your monthly payments will jump to $1,611, or $361 more per month. Hopefully, your income will have jumped accordingly to support the higher payments or you have refinanced your loan by that time.

Mortgages with interest only payment options may save you money in the short-run, but they actually cost more over the 30-year term of the loan. However, most borrowers repay their mortgages well before the end of the full 30-year loan term.

Borrowers with sporadic incomes can benefit from interest-only mortgages. This is particularly the case if the mortgage is one that permits the borrower to pay more than interest-only. In this case, the borrower can pay interest-only during lean times and use bonuses or income spurts to pay down the principal.

A graduated payment mortgage is a loan where the payment increases each year for a predetermined amount of time (such as 5 or 10 years), then becomes fixed for the remaining duration of the loan.

When interest rates are high, borrowers can use a graduated payment mortgage to increase their chances of qualifying for the loan because the initial payment is less. The downside of opting for an smaller initial payment is that the interest owed increases and the payment shortfall from the initial years of the loan is then added on to the loan, potentially leading to a situation called “negative amortization.” Negative amortization occurs when the loan payment for any period is less than the interest charged over that period, resulting in an increase in the outstanding balance of the loan.