This will diminish the short term benefit as you would pay full taxes now on that contribution, but 12% growth compounded over 25-30 years would be a really huge pile of tax-free money from which to take distributions in your retirement years.

The UPB is the asset which is diminished monthly by the principle, and interest is classified as income. 

After a few years the IRS ability to Audit is diminished with time (approximately 2-3 years) and the trust will be "Old and Cold" and we could continue to sell and conduct 1031's at that point.

Once it drops you will be stuck holding with diminished returnes.

I know that if I waited any more, he will feel like he has some extra money in his pocket this week which will diminish and delay me further. 

Historically, this area has had a supply demand imbalance and with the continued tech concentration, I don't see that diminishing anytime soon.

What you'll find is your return is higher when you leverage your money.Here's an example of a property I analyzed recently for another investor:Notice the highest return on my investment is the first year and it diminishes after that.Also notice I have $103,067.64 in equity on year ten.

I disagree, cash on cash is always relevant even if cash on equity diminishes.

I've been interested in it though since I was very young maybe 12, but that all kind of fell apart and my interest diminished somewhat in my later teenage years.

HELOC interest rates are based on the prime rate from the Fed, and since the Fed has dramatically cut down the rate, the profit margins for banks have diminished.