I don't know the FHA answer but I would advise you to make sure the two properties are on two separate legal parcels and if they are next to each other have a survey done. 

Already run 300+ nationally but as a separate entity. 

This changed my approach to 1) Always assume the taxes will increase after the transfer. 2) I now write in an addendum to purchase all of the personal property separately.

That is completely separate Why  is tenant blaming landlord for an act of God and something out of the landlords control ?

Property is listed as a SFR but could easily be converted back to a duplex with separate entrances. 

Can you separate the top from the bottom? 

Is the property a single house or is it segregated into two separate units (or easily segregated).

Three separate businesses, underwrite each one separately.

Any time you obtain a property without title insurance you are retaining that risk.Title searches mitigate a lot, but not all of that risk so we get them any time we are purchasing properties without title insurance and have them done by our title company instead of a separate service provider.

Like a separate dining room that never gets used or space in the basement?