OK I finally got around to doing some of the math myself.

I also listened to the podcast.

I've done the Excel and it does help.

But: "you have to spend less than you earn."

Also you should consider 3 scenarios. (Yes I am ignoring the investing scenario.)

1) 30 mtg do nothing

2) 30 mtg make an extra 10K pmt at the END of the year

3) 30 mtg + Heloc, make extra 10K pmt at the START of the year

Assume 100K borrowed, 3.5% interest, pmt 447$

HELOC also 3.5% interest, paycheque $4000, expenses $3000 (including the mtg pmt)

Assume paycheque on 1st of month and expenses due on 15th. (results would be slightly better if you can push your bill pmts to the 30th)

So here are my results

1) total interest paid $61000, paid off in 30 years

2) total interest paid $14800, paid off in 8 years

3) total interest paid $12900, paid off in 7y 1 month

The $12900 includes about $12200 for the mortgage PLUS $700 from the HELOCEvery year the HELOC does this crazy sign wave where it starts at -10000, jumps up to -6000, crashes down to -9000 and repeats every month slowly climbing and there is a bit of interest too.

The HELOC balance actually becomes positive at month 7, but then falls below zero again. +ve -ve for months 7,8,9 and is finally totally positive at month 10. (This might be the basis for some arguing above.)

So, in summary, if you plan to pay an extra 10K every year there is only about a $2000 and 1 year advantage. With the HELOC method vs stash and pay at the end.

Is this worth it? If you can't figure it out, don't do anything financially you don't understand.

I think the extra 10K HELOC is hair on fire debt that would keep me focused on paying it off and therefore paying my mtg of faster.The HELOC generally has much better advantages to a checking account. (Again do your own research and understand the difference.) Close your checking account, especially if it charges you fees every month and makes you keep a minimum balance and charges you for cheques. Also if you ever use overdraft the HELOC is much better, usually pennies interest vs ~$50 in fees and interest.

About 10years ago an account friend said he uses a HELOC instead of a checking account but keeps a positive balance.

I never really took the time to figure it all out.

The only negative I see is if you may be tempted use the HELOC to spend above your means for travel, cars etc. I've had a HELOC for 5 years and never abused it but never really put it to work for me either.

I plan to use this method when we refinance our rental property. I'll keep you posted.