I repeat, there is no magic in this. It's all about how much additional money you commit to paying down your mortgage/line of credit. The online calculator sited, for instance, asks how much of your net paycheck you save, but the lowest amount allowed is 10 percent.
Most people do most of their saving through their company plan and many people don't save enough to capture their full employer match. So saving a minimum of nearly 10 percent MORE (yes, it's after-tax 10 rather than pre-tax ten percent) is a big deal.
You can see how big a deal by making some comparisons. Suppose you earn a good income and have $10,000 of takehome pay monthly. That's a total of $120,000 a year, of which you save 10 percent or $12,000. Suppose also that you are very conservative in your home buying and have just bought a house for $400,000 with a $300,000 mortgage at 6.25 percent. Your monthly mortgage payment would be $1,847 and you would pay the mortgage off in 30 years. You would also have a choice about what you did with the additional $1,000 a month. You could invest it elsewhere or you could add it to your mortgage payment and accelerate the paydown of the mortgage.
My calculator says that the extra $1,000 a month would pay the mortgage off in 12.77 years.
Now lets use the same monthly figures in their online calculator for THEIR line of credit loan which happens to have an APR of 7.72 percent. Again, when you take out their line-of-credit/mortgage you make a monthly payment of $1,847 and you also reduce the credit line by an additional $1,000 a month. Their online calculator says your loan would be paid off in 14.2 years instead of 30.
Note the difference. Make additional principal payments on a conventional 30 year loan at 6.25 percent and you'll have it paid off in 12.77 years. Make additional principal payments on their higher interest rate line-of-credit loan and you'll pay the loan off in 14.2 years instead of 30.
As I said earlier, the most important thing here is the amount of extra money applied to the loan each year. Everything else is window dressing, marketing and hits at magical results from your cash balances. If the amount of money available to be saved were smaller, the shortening of both mortgages would be much diminished.
Yes, there is some advantage to using your full monthly cash flow to reduce the principal balance somewhat through each month. But this not that big a deal. Remember, the mortgage is $300,000 and the monthly cash flow is $10,000, of which $1000 goes permanently to loan reduction. So the interest you are saving on cash flow is whatever your cash balance is through the month--- some fraction of $9,000. It's a nice touch, but it doesn't appear to overcome the higher interest rate over a conventional fixed rate mortgage.
Scott