So, lets do some math.... for comparison reasons, I'm using the current rates from Freddie Mac... At this point in time, the ARM rate is higher than the 15 FRM rate. From January 18, 2018 to January 24, 2019, it was the ARM rate that was lower than the 15 year FRM. It switches back and forth. Now, using those numbers, lets compare a 15 year verses 30 year mortgage using the same base amount of $200k (it's a nice round number)... So, assuming you just do the payments without adding more to pay off the principal, you are paying $484.19 more per month (not double because of the interest rate discount), but in the end, pay $74,301 less in total interest payments. As for our ARM friend... The big thing is that you have to be able to afford the mortgage payment. There are people who purchase a home and forget about the other expenses of owning a home, and get into trouble. Each person's situation is different. While I realize that there are investment opportunities that are available, I also want to get my mortgage down. In case of emergency, I can spend the $250-5300 to recast my mortgage and get lower payments.