However, a lease carries a lean on it and will stay with the property until paid and also its value will not be considered in the home appraisal like a cash or loan array will be. 

And add the political climate, with rent control state wide now in Oregon and possibly next in California. 

You may want to find similar minded investment partners or perhaps find people different from how you think so that way you get a diverse array of opinions on investment options.

La Quinta, on the other hand has few if any regulations city wide, but all the HOAs usually severely restrict STRs and those HOA rules can change even month to month. 

For my having a wide open use like MF to Warehouse limits the cost estimation.

It seems too low, so as a double check, I just looked at MLS for active SFR listings county wide. 

A new single wide down south on land was $35k. 

The idea is to consider the single-wide as the "primary" unit (that's how it's being sold) and apply for a construction loan to finance both the primary unit (the man home) and the future ADU. 

Many associations have restrictions on the number of rentals allowed in the complex and certainly on short term rentals (both complex and city/county wide).

The investment of a solar array on a house will mean different things for people in different areas in terms of a higher resale value, so while you may have not seen it in your area, there are other areas where it is highly desirable and will command a premium.