Trenching, utility connection charges and etc. add a huge cost handicap which makes the economics unworkable in almost every case. 

Local market economic conditions. 

Unfortunately, I suspect we know what's going to happen to them especially if there is any downturn on the lower economic rungs because of tariff wars or similar.

Regardless of paper returns, as you noted, these are the homes located in areas that suffer first and the most in an economic downturn or other times of distress. 

Those that deal with the 12 1/2 % remaining have a chance for much better success OVER THE LONG TERM, in all economic environments.  

But separate disconnected units wouldn't be economically efficient or even feasible for assisted living care once they need it. 

One thing we, as humans, are consistently bad at is predicting the future - especially when it comes to political and economic shifts. 

So you want to keep a good insight to that and what kind of economic changes that could bring. 

I know plenty of folks who meet your definition of Ultra and they seem very happy to me and have loving families although they also have the same struggles with kids that every family in every economic strata has.

He is enticing people into paying more than the minimum, it is no more complicated than that.Pay mortgage payment = 22 years of payments (in his summary)Pay mortgage + HELOC principal + HELOC interest = 9.6 years of payments (in him summary)There is nothing wrong with it, it is behavioral economics.