I am in the Southern Maine area if that mattersGoal and costs : So I am looking to purchase land and build a 50x100 metal building for dry storage which will on average produce 10-15K per month profit after expenses.

There are many uses besides dry cleaners or gas stations that can pose environmental risks. 

Foreclosures skyrocked, unemployment jumped to over 20%, all the businesses that lost their clientele, customers, etc. from all the building related unemployment (brokerages, insurance companies, sub contractors, material suppliers, title companies, appraisers, sign shops, printing companies... cafes, hair salons, etc...

I just sat through the whole webinar and a lot of what he said was true about retail buyers entering the market, hedge funds buying in bulk, reo's drying up, spending time analyzing deals, etc...

Note; paper underlayment will be cheapest, but it's cheap for a good reason, and it's not its robust life expectancy...The strapping you mentioned is a slight added cost, but if done properly (vents at the eve/drip edge and ridge), can actually help lower inside attic or top-floor temperatures, as you now have an "air gap" to help alleviate some of the penetrating UV heat, as well as helping to drain and dry condensation that WILL form on the backside of a metal sheathing.

My broker said loan products he represents for STRs just dried up. 

Use a mask while painting large areas so you don't get high off the fumes.The entire house had dried, chewed up gum throughout the floor and walls.

I also try to dedicate about an hour to just thinking out side the box of creative ways to build a lead pipeline (PPC, Divorce Lawyers, Landing pages, Door Knocking, social media ect), that is your business essentially so make sure you create many for yourself so if one dry's up you have a few others to work off of until you can gain another.  

I see issues with it all the time, even in PHX where it's hot and dry all year round.

Just not always cut and dry.