If it's too much disruption to my quality of life then I pass. 

Kevin Polite I presume Zillow's strategy is to disrupt this space and thereby ultimately lessen MLS grip on the RE market.

If you're ONLY interested in it as an investment, and NOT in disrupting your current living arrangements, then you ONLY have the conventional route option, not FHA.And if you "assume all units are rented out, non-owner occupied", and it STILL "cash flowed negative/break-even when analyzed using 50% rule", then will it be a good investment after you move out, anyway?

If for some reason I can't or don't close it's very disruptive. 

Now that Amazon is getting into groceries with same day deliveries, I wonder how much will that disrupt traditional grocery chains and their supply chain since commodities have a more limited shelf life.Amazon is a disruptor to the grocery industry

You may have to deal with pet, smoking, drugs, non payment, divorce, firearms, abusive tenants, physical damage, unemployment of tenants, physical disablement, disruptive children, disruptive visitors that come and stay, fire, natural disasters, management, all or some of the above and much much more.

In addition the office of building is saying that the only way this could be considered legal and conforming is if this property was functioning as a duplex since 1954 without and 12 month disruptions in either of the units.

Another point is that the really old houses were not built to be super tight, and sometimes using closed-cell foam makes them a little tighter than they can handle (like having one to many ;-) ) and you have an acceleration in the rate of deterioration.Insulating and air sealing are disruptive undertakings - the degree of disruption can vary and will act as a limit of the degree of insulating or air sealing you can obtain - but in our experience, you can achieve 40 - 60% of the desired/possible improvement with minimal impact.

I am going to let that one slide so that I don't allow you to disrupt the discussion.

There are sleep disruption issues 7 days week.