I dont know why he makes it sounds so complicate. Basically, you are obtaining a low interest investment loan secured by your house.
This would work under a few assumptions:
Your return on the investment is higher than the interest you are paying on the line of credit you get from the mortgage (this year would be a bad year to do this)
The value of your home doesn't go down significantly.
As he said, it is a good way to leverage because of the low interest rate than conventional investment loan. You just need to watch out the return of your investment and the total facility of your LOC, which might subject to the value of your real property.