Most times, the due diligence period is used for you to bring out your inspector to physically test the property (environmental, structural, roof, etc.) 

Most markets the physical vacancy is 5-10%, good chance you can find it by googling and seeing what the average is.

In this scenario, I physically couldn't accept Section 8 because the house didn't have a legal rental permit.

Just curious, I’m a big magazine fan (physical copies).

This setup allows me to maintain my current income while being physically present in Missouri to actively manage our real estate investments.My BRRRR Strategy:My goal is to identify single-family homes or small multi-family units that need some rehab work, ideally in neighborhoods with strong rental demand and growth potential.

What other factors should I pay close attention to in either the deal or when reviewing the physical property?

This ended up being a wholetail where we physically closed on the property ourselves and relisted it on the MLS after bringing up its market value.

I own a few online businesses and in negotiations to purchase another local physical business within the next month or so.

Personally, I've seen tenants granted a continued occupancy/renewal of their lease for the following:(1) threatening other tenants/neighbors with physical harm(2) dealing drugs out of the apartment with children residing in the same building(3) discharging a firearm on the premises(4) refusing entry to the landlord/his agent for necessary repairsAnd I am sure there are many other examples of bad behavior that the property owner is powerless to react to.

They are not generally near a retail center-point so I'd be curious who a potential solid backfill would be, especially to your point, given the size and physical attributes of buildings themselves.