It looks like in Baltimore county, you can't rent out an ADU unless it's to family members. 

longboat key limits most rentals on the island to 30 day minimum (that does not mean you can't rent it to them for the whole month but they only stay one week) our complex also limits how many times a year you can rent it out. 

My questions here would be around the anticipated appreciation and any potential for improvements - either forcing appreciation or increasing rents.

Stay away from anything that won't rent well in down markets such as we are in right now.

I "flipped" the house I used to live in (and rent rooms out of), and currently run an Airbnb in my second house. 

There are so many new posts on BP about the same topic (eg tenant didn't pay rent or tenant is late on rent, what do I do). 

Hi Daniel, Would you be utilizing one of the units in the duplex as a primary residence or do you plan on renting both units from the start? 

Now, had he let the guy move in, collected the rent, and not paid me, I would have sued him and put him in jail without hesitating.

Rent bedrooms. 

Consider all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.