Also, providing value to others at a high level will pay off for you in the end if you stick with it.

Namely, that if a tenant (in this case accompanied by a whole family) ends up stop paying rent and I would be on the hook for both covering the mortgage and dealing with open ended legal costs and time.

You don’t have to pay $20k+ to learn to broker loans. 

If you have cash, you could pay off the underlying loan2.

I don't know the rules in the US, but in Canada, you can do that every 2 years and when you sell, you don't pay taxes on the capital gains.

You don't provide enough data to know.Every product is only worth what you are willing to pay for it. 

This is a the perfect vehicle to use for short term like buying a  property with cash, then refinancing the property to pay the line of credit back in full, and use it again.   

If not, who do you believe the natural buyer is and why do you believe they will pay retail when they can replicate what you accomplished with any number of available properties on the market at any given time?

But, the self-sufficiency test for FHA loans can be really difficult in SF, meaning that the market rent from units you will not occupy must be sufficient to pay for the mortgage payment. 

Why pay off the mortgage early?