@Aleksander Dabrowski As you move forward a word to the wise depending on what configuration of rentals you end up with put in a ban on portable washing machines and dishwashers on all floors that have a floor underneath them.

I'm sure we will run into the issue that it is cold in apartments on the 1st floor and hot on 2nd/3rd which will result in tenant complaints and/or upstairs tenants leaving windows open to regulate their heat (I had this issue in a similarly configured 5-unit building).  

Next you configure what day a late fee is added and check the option that doesn't allow your tenants to pay partial payments on the system.

Zillow may or may not be aware that a listing has expired, property has sold, etc.The "Zestimate" is their software's best guess based on available data for recent sales, current listings, etc. for properties of similar square footage and/or configuration.

Are there savings on a construction loan for this configuration as well?

We are leaning towards putting an addition on the back of the house changing up the configuration and turning it into a 2/1.

Depending on the configuration of the property, the expense of sub-metering should be considered to determine the ROI. 

So, depending on the configuration of this duplex, it may meet the new requirements/definition of a legal ADU or JDU. 

A good vendor will help you get the proper camera for each location...they have various focal lengths, day/night capabilities, license plate readers, and analytics (that can automatically send you an email when an area is entered during a specified period, such as late night, great for catching trespassers) that are pretty easy to configure for common needs.They do not come cheap, but OTOH they give you eyes 24/7/365 and are generally very low maintenance.

You can custom-order them with whatever features/configuration/materials you can think up and they prepare a custom quote.