As for unusual STR rentals we stayed in a converted grain silo in Ohio but wouldn't recommend, nicely done but cold.

Property is right outside of a Natl Park in CA, and we'd like to use it as a full-time STR/ AirbnbI'm comparing DSCR loan options today (no DTI - DSCR is my only option), and notice that 10 year I/O options boost my cashflow, but am uncertain if this is better than your standard 30 year fixed.

Sourcing and managing contractors is inefficient, stressful, and highly uncertain for the owner...and also inefficient with serious service quality challenges for the contractors. 

It was unusual to receive that warning given they haven’t grown that much tall.

Cash flow is a means to stabilize the asset and is essential to cover your back in uncertain times. 

As a RE Agent now myself, I thought it was unusual to not see their pic on their cards.

It's a somewhat unusual setting in that these duplexes are sitting on a block, that is very highly elevated from the street.

So,  sorry for the long story,  but it's a bit unusual.  

Are there any unusually annoying noise disturbances from factories, airports, highways, etc.?

The 80% / 20% rule of leverage does not exist as a cruel and unusual way to complicate the lives of real estate investors.