Here is a basic break down of how this works.
The interest rate is pretty much irrelevant.
Basic facts :
Primary mortgage. Equals 200k
Salary equals 5k.
Total monthly expenses equals 3k
HELOC equals 20k in second position
So lets start this off.
First let's pull 10k out of the HELOC and put it on the principle of the 1st mortgage.
First mortgage = 190k
Heloc= 10k balance
Month 1
Then let's put your entire paycheck in the HELOC acct. This accomplishes paying the minimum payment on the HELOC.
HELOC= 5k balance
Now let's pay your expenses from your HELOC.
HELOC = 8k balance 5k(balance)+3k(expenses)
Month 1 balance
Primary mortgage 190k owed
HELOC 8k owed
Total debt 198k owed
Month 2
Put the entire paycheck in the HELOC
HELOC balance 3k owed (8k-5k)
Pay expenses of 3k
Mortgage Balance 190k
HELOC balance of 6k owed (3k+3k)
Total debt is 196k
Month 3
Pay expenses 3k
HELOC =9k
Put entire check in the HELOC
HELOC = 4k
Mortgage Balance owed 190k
HELOC = 4k
Total owed 194k
Rinse and repeat......
In month 5 your heloc balance owed will be 0.
Month 6
So in month 6 you put 10k from your heloc on the principle of your primary mortgage.
Primary mortgage Balance 180k.
HELOC balance is 10k
Total owed is 190k
Put your entire paycheck in the HELOC
HELOC balance. 5k
pay your expenses 3k
HELOC balance is 8k
Primary mortgage Balance is 180k
Total debt 188k
Month 7
Put entire paycheck in the HELOC 5k
HELOC = 3k
Pay your expenses 3k
HELOC balance is 6k
Mortgage Balance is 180
Total debt is 186k
At the end of one year your principle balance will be 180k . Not bad for living the same lifestyle and still have access to some cash.
Rinse and repeat until your debt is gone
It really is that simple.
The extra open credit (10k) on the HELOC above the 10k in this case is used as an emergency fund.