Double payment on a 30 yr mortgage

[Marty Sheehan]

I ran a hypothetical mortgage payment on a calculator and found that when making double payments (one normal and one principle only) on a 30 yr mortgage you pay less in interest then single payments on a 15 yr.  I hear a lot of investors on here using a 15 yr mortgage as one of their criteria.  Can anyone who does this explain why they would use a 15 yr mortgage over making double payments on a 30 yr? Is it taxes, expenses, just simpler, etc.?

[Sean Grapevine]

15 Year mortgage payments aren't double the amount of 30 year mortgage payments. Take for instance this scenario on a $150,000 mortgage:

30 Year @ 4%:

Monthly payment: $716.12

Double payment: $716.12 = $1,432

Months to pay off: 130

Total payment: $186,160

and then this scenairo:

15 Year @ 3.25%:

Monthly payment: $1,054

Extra payment: $378 = Total of $1,432

Months to pay off: 125

Total payments: $179,000

Savings: $7,610

Yearly savings: ~$760

I honestly thought the differences would be more stark. You're basically paying $7,500 for the option to have a lower payment, which may be a worthwhile trade-off for you.