Also having defined processes for risk analysis and property vetting has been extremely helpful in vetting new acquisitions. 

I am planning on implementing something similar to your suggestions of post occupancy, defining move out date, and have a month-to-month lease in place that would go in effect for paying rent beyond that.

I have found up to four "units" but I don't know what they define as a unit.

@Michael MitchellCreate a multi member LLC and have the breakdown illustrated in the operating agreement and define who does what and how people are paid.

The property is absolutely beautiful, and the house has so much character.

So, you can perhaps define price ranges and use that to profile the different areas of a market.

that she paid rent otherwise the lender will define her as "homeless."

Now, if out-of-scope items arise, like the electric, it's processed via a change order which again, has an exact defined $ amount, time etc.. 

@Parth Patel It varies depending on your state/jurisdiction, but for the most part, STR's are defined as stays of less than 30 days.

That said, I do like the structure of having a defined business with an EIN and a bank account that is really run like a business and files tax info for all the properties in one place consistently from year to year, and it seems like a general partnership might be the way to combine these options.I don’t mind filing a 1065 and might even prefer it over putting all the details on our 1040, so I’m not trying to avoid that particular complication.