In general it is not worth building a single ADU for a variety of issues but the largest is the cost to add the ADU is typically far greater than the value added by the ADU.  

Here's my take on the decision:First, let’s look at the pros and cons of paying off your current short-term rental (STR):Paying Off Your STRPros:-You Eliminates your largest fixed expense (the mortgage), which increases your cash flow significantly.

I'm from Long Island, currently looking for a deal myself

For example, in the New York area, especially in some hyped-up fringe neighborhoods (like certain areas of the Bronx, Queens, or Staten Island), finding a "bargain" seems easy.

In HI there are leasehold properties, cesspools, water catchment, and Lava Zones (on the Big Island). 

my wife if Norwegian  Wika   :)  raised on a little island in the Columbia River and family were all fishermen and loggers.

There is land and markets available in the DFW area.8. 

And although many investors say they are only looking for off-market properties, the largest buying list is still the MLS. 4.

* What do you do to ensure that the tenant is responsible for security deposit disputes since that is the largest reason for owner lawsuits* How familiar are you with the newly changed laws that can affect you the owner if they are not used correctly?

We spent 2 months on Madeira last summer, and 1 week on Porto Santo and loved every minute of it so I'd like to get a few properties on the Island and eventually relocate there.