I do know Mike personally, and we've altered the agreement based on the feedback others provided earlier (see my last comment). 

It could be an illegal duplex, meaning someone converted a single-family without permission and/or in violation of code.

Smart locks are good for this, until they aren't : ) But if the tenant has wifi you can do smartlocks and give codes to contractors that are good for X hours then expire.  

You cannot use older properties as a model as they are grandfathered and do not have to abide by the new code. 

My dad and I fixed it up over the last two years, and it has passed all its inspections and meets the code requirements for me to get a renter in there.

If the agent isn't responding to your agent then he's likely breaking the Realtor code of Ethics, and Bright MLS rules, requiring clear cooperation.

The tax code is so complex that no accountant can understand every aspect of the tax code. 

You are also venturing into areas of building codes and zoning codes that could put a damper on your plans.

I don't think the PO cares, just your tenants.If you can do this then you should be under cover and fine unless you have a real aggressive building code enforcement or someone complains about something.I know of an effort in Savannah to make a duplex like this to code. 

Insurance is for catastrophic life altering events.