I've never gone through the zoning change process that you mention although I've heard it can be very profitable.  

Not to mention the very long list of the horrors that density of housing combined with poverty has brought all but 100% of the time over history. 

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.

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

I like the areas you mentioned - they look solid. 

They are clickbait as Colin mentioned but also oversimplified. 

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

There is a competitor in my market, talking with the owner he bragged of this model I mention above.

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

Now that you mentioned this, I looked into it and, at a glance, they offer "Full-Service Maintenance Coordination", which offers the phone answering, troubleshooting, etc.