I don't have good 'rule of thumbs' for you there on a per unit (for instance per foot) cost. 

There is however case law to go by from previous instances.

For instance, my mom-in-law fell last June,  hospitalized, and stayed with us till 2 weeks ago.

Nancy Zhao Depends- in many instances property values fell dramatically.

In the instance of a BRRRR investment, and the owner is able to cashout his principle up-front, would it seem fair that (assuming a 15 year note), I would get the same proportional share on the property once it's free & clear in 15 years or if the house sells?

I know that many people who "house hack" call themselves investors, but I realize now that because they live in the home they are renting out (a portion of) they are not really investors, they are just tenants who are in the process of buying the home (at least in that particular instance with that particular property).  

I would also confirm with the County that they will accept a payment plan as in most instances once they become past a certain point they send them to tax sale, so definitely talk to the county

(Prices in the last decade have been a few years behind Denver.)A lot of people are interested in the Midwest (me and my wife, for instance), but if you're looking for something close to home, it's a good play. 

While I agree most customers do not have contracts, there are fairly common instances where customers do have contracts.

For instance, a buy-and-hold investor who's criteria is 8% CoC return will value something differently than an investor who wants to achieve 12% CoC return.