However, I did instruct her on how to send it in the future and warned that if it was sent incorrectly, she'd be responsible for the fee I incurred. 

Who is reviewing the title prelim, specifying fire and liability insurance requirements, providing lender instructions to escrow, and recording your deed of trust?

There is also a solid base of smaller companies servicing these sectors- healthcare, financial services, manufacturing.  

Potential issues that you might want to look into are zoning, the structural stability of the building if it is multi-story (flooring, people, appliance add a lot of weight per sqft).Depending on what type of construction the warehouse is (Pre-engineered metal building, block, bar joist, or structural) you might have good luck partitioning areas off for contractors, light manufacturing, etc.

As a a manufacturing engineer, and by no means an I a REI expert, I can tell you that with your education and thought process you are already about 10 steps ahead of most people when it comes to the analytics side of this biz. 

Twenty million Americans live in mobile, or manufactured, homes that offer affordable housing, particularly in rural parts of the country.

Knocking on doors when the agent (as instructed by the owner) forbids it, is A) rude, B) could be trespassing (I get there may be little if any consequences to that), C) could get violent (I'm confident you would not be welcomed at my front door and would be met with swift and decisive resistance), D) could get you into trouble with your local Realtor board, and E) could get you blackballed on the deal.

@Jane S.When A tenant thinks they have ownership of the building you need to get a tax bill ,an insurance bill a the mortgage statement .etc then Hand them that big stack of bills and instruct them to pay up .When they say “what’s all this for ?

I did a little checking and, indeed, I think I can get a parcel for $50K, and a decent used mobile/manufactured, in need of updating, for $25K.I think a septic could be done for less than $10K. 

The current house on the property was manufactured before that year and the bank will not finance it for that very reason.I would like to talk to the owner/ real estate agent about owner financing.