If this property is historical in the sense that it is on or may be placed on a historical register, the renovation project will also have to conform to a set of conditions that will generally have to do with maintaining all or significant portions of existing architectural elements such as facades, building materials and colors.Historical or not, any planned project will have to be heavily vetted in terms of existing conditions and projected uses for all major building elements such as structural, electrical, plumbing, mechanical and ADA and ANSI provisions.

Decided to try what @Wayne Snyder suggested for Ada County, The county assessor website does provide gis files for all parcel within the county as well as unit counts for each one.

Also, an I'm only speculating here, unless the unit(s) are ADA accessible you might not need to provide an accessible route. 

I plan to make a unit ADA compliant.

I also think most landlords don't realize that ESAs are not covered by the ADA, only Fair Housing, and that the landlord does have the right with service animals, if the disability and need are not readily apparent (i.e. a seeing-eye dog), to ask the specific function of the animal and documentation that the animal is a medical necessity.

@William Coet there are a variety of reasons at play and interestingly enough for the past 2 years or so I am getting $700k per SFH partially because they changed some of the regulations specifically for people with developmental disabilities where they now want the SFH to have Fire Suppression systems and sprinklers as well as ADA requirements.There was a few lawsuits in NJ that have really helped make affordable housing possible.

https://www.idahostatesman.com/news/local/community/west-ada/article231044388.htmlCaldwell approves 187-home subdivision.

ADA height and elongated.

The process would be to first have an Architect put together a feasibility study to determine what can be built based upon the properties existing conditions, zoning requirements, code requirements, ADA requirements, and the desired use.

I don't know if they have info re Emotional Support Animals (ESAs)And, if you have questions re SDs, you can call the ADA hotline-they have an 800 number.