I did find a couple of investor friendly insurer options on this site so hopefully that bears a couple good options.

We Specialize in Conversions and Ground up Builds with fully Prefabricated Off Site Construction How did you find this deal and how did you negotiate it?

Start visiting building sites so you can meet the trades and see finishouts in different price ranges. 

I would not approach it from the standpoint of I want to build container homes and then look for a site, I would have a site and think about what the best use of it would be and if it happened to be container homes then go for it.As John mentioned above appealing to the masses is the route to success here IMHO

Most of my guests will go in and tell the restaurants /shops that they are staying with my glamping site for 10%.

Does anyone know of a reliable site or resource to check zoning laws for Airbnbs or STRs in general?

Think of it like a dating site in that its purpose is to just bring the interested parties together, but if love is to bloom, it will take some work.

Applicant is ok to show me in person his account information on his laptop, but doesn’t want to put his user name and passwords to those sites into RentRedi application.

HUD publishes the Median Fair Market Rent on their web site for the entire country.

I would make a site visit to where they live now and see how they treat the current property.