The tax advisor you are speaking with will call it that because they want to demonstrate their value but all they are doing is following the tax code.

Current building code requirements and local amendments should be considered forrebuilding the fire-damaged portion of the residence.The Engineer shall have no liability to the Owners, or to others for the acts or omissions of theContractor or any other Persons performing work on the project, or failure of the Contractor tocarry out the work in accordance with this letter, except where specifically inspected andapproved by the engineer and discovery of defect is possible within the normal ability or standardof care for the industry.This report is based on a diligent visual inspection of the referenced areas.

There are some general rules but there is also room for flexibility built into the tax code depending on your specific tax strategy.Is your duplex separately metered?

Yes, Chicago has strict regulations for short-term rentals, including mandatory registration and zoning restrictions.

It depends on the zip code and the specific property.

So, you're not "wrong" in thinking it's complicated.The tax code plays heavily into how certain transactions are categorized and there is some flexibility regarding what we can capitalize versus deduct.

Strictly speaking from a financial point of view multi family's almost always make more sense unless your walking into some equity in a single family.

Be sure to check permit and code requirements.5.

It puts each expense in the appropriate IRS code and punches out year end summaries that I email to my tax team. 

You MAY be able to ensure nobody is living there and avoid the need to use a constable/sheriff by having the municipality's code enforcement office post a notice saying the place is "uninhabitable".