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?

To pay for this, I used a heloc on my current home.

Why pay off the mortgage early? 

@Parmesh P. there is no such TDA paying 7% or even 6% long term,5 years or longer.

In 2020, the ground leveled out, then quickly shifted to hilly terrain.

Make sure the tenants are paying market rent or above, otherwise your loan will be DSCR constrained.

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. 

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.

Don't pay the current owner (higher purchase price) for the work he/she didn't do.

I LOVED getting a loan through DR Horton on a DR Horton build, that I had to pay for a DR Horton appraisal.