You can also test for formaldehyde, Volatile Organic Compounds (VoCs), arsenic in the water, DFAS, gas stove fumes, microplastics, fecal contamination, and so on and so on.It is worth summarizing it this way.  

What Works Best?

Consider working with local agents familiar with these markets to identify the best opportunities.

Historically, the "...best time to purchase a home is always five years ago."

This is very important information, depending on how your agreement is set up this may be a way to exit the agreement. 

My last rehab was projecting far better than a 2 to 1 return which was fortunate because we went way over budget (my worst over budget by far ever).

Listening is one of the number one assets, so if theres ways I can contact other real estate investors and learn from them would mean alot.

CA is hard all the way around with real estate, but if you're willing to jump through the hoops, San Diego is a good place to have a STR in a CA city.

The issue we often run into is the pure cost to build...you have ideas or ways you are working around that?

What are some ways I can verify that tenants are protected throughout the entire lease?