In many cases the 40 year amortized loan will have a better rate than an interest only payment. If the 40 year payment is just slightly higher than the interest only payment, opt for the 40 year payment because you will be paying down some principal.

The 40-Year Mortgage allows for principal reduction but at a significant lower payment to borrower. The difference in payments can be pretty significant. For example, on a $500,000 mortgage financed over 30 years at a fixed rate of 5.875% costs $2957.69 a month. But the monthly principle and interest payment drops $2707.63 on a 40-year schedule. That is over $250 less in your monthly payment.

One of the disadvantages of a 40 year loan is that the homeowner builds equity at a much slower pace. For first-time buyers counting on equity accumulation to eventually move up to another, larger and more expensive home, this slower pace of equity accumulation is a liability and may leave some people sadly disappointed.

For renters who cannot afford a 30-year mortgage and still want to own their own homes, a 40-year amortization mortgage is often a good solution. In many metropolitan areas, the average rental cost for a single family residence is about the same as the monthly payments of a 40-year amortization mortgage with conforming loan amounts. Renters in these areas can often afford their own homes afterall. However slow homeowners with 40-year mortgages build equity, they do contribute to the equity of their own home nonetheless.

If you run the numbers using a mortgage calculator you will be able to see the benefits of homeownership vs. renting.