Occasionally I catch some cleanliness issued that I am not satisfied with which I believe is due to variability in attention to detail between people on their crew, or lack of training and familiarity with my property.I've seen mentions of the value of post cleaning pictures from hosts on other forums.

I agree with Erik, although their are some investors out there that will help fund the down payment/entry fees that you mention, they typically are friends and family that trust you and believe in you.

I saw someone else in the forums mention a site called www.rocketlease.com but it is $35 vs the site you are mentioning costs $25 for seemingly the same services.

I wouldn't build the ADU just yet because like it was mentioned it cost more than you can really make a good return on.

One option I haven't noticed being mentioned is to auction it.

I like the areas you mentioned - they look solid. 

The things you have mentioned are simple, high level thoughts based on assumptions.

As you mention, if you are using hard money yes you are paying more in interest and if you hvae the cash I would recommend using cash over hard money due to the high interest rate that you are paying.

I was unaware of the tax-paying requirement you mentioned for adverse possession.

As Miguel mentioned above, a majority of the time MTR residents do not search for housing in advance.