I did not see any distinction between adults or children when someone is considered as an occupant (other than 12 months or younger) they don't count, or at least here in MA.  

The advantage of a duplex is that it acts a lot like a SFH as compared to an apartment which gives you a distinct advantage when renting. 

There's a big difference for you and an investor, This will determine if someone buying today will be coming from an investor pool or an end-user Owner Occupant pool. 1) Possible scenarios not listed is you may accidently come across someone trying to place 1031 money last minute and will do the deal.2) You have two distinct groups of property, 7 of them are Class A/B+, and 9 of them are Class B-/C, maybe you sell the B-/C properties to the investor community in bulk which would be easier if you didn't have the Class A/B- properties that won't make any investor any money, just sell the higher class 5-7 properties to OO's.

The distinction needs to be made more clearly. 

After we purchased the property, we adding fencing to create two distinctly separate homes.

There are two distinct reasonings behind each of those methods. 

They are subject to completely different tax regimes - and require distinct approaches towards tax mitigation. 

With a total investment of 347k our Total cash on cash return is around 14%....but it's passive and we'll have distinctive tax advantages with Real Estate.

There is a distinction between "assistance animals" and "service animals." 

As other have mentioned, on Airbnb you will have to bake the tax into your nightly rate (if they do not automatically remit, they don't have a mechanism to separate out the tax as a distinct line item).