The company I used was at http://decals-oem.com/specials/18x24.htm. 

Generally,  unless there are additional restrictions set locally, Mary  may move in to that commercially zoned area since her residential use is higher than set by zoning.Now, if Mary starts a trailer manufacturing operation, building utility trailers, she will most likely be out of compliance  with the commercial zoning, since manufacturing is "industrial" use which is the lowest use category (light and heavy industrial and those are broken down to specific operations as well).

The store at the mall doesn't typically buy directly from the producer/manufacturer.

I'm sorry, but I can't understand your sentence regarding Cleveland.Cleveland, Youngstown, and the rest of the rust belt all declined for similar reasons--the loss of manufacturing jobs, which were the driving forces of the economies in this area.

Known as democracy of Arms in ww2 (educate yourself why they received that name) Number 1 for Manufacturing in USA Infrastructure of Detroit and even surrounding suburbs is built for manufacturing, trucking and import/export. 

Anyone have advice on manufactured home foundation issues?

They have GE OIL & GAS building gas appliances BRIDGE STONE TIRES MANUFACTURING, A new Solar panel Manufacturer,,  many new businesses at Cecil Commerce.

Let me know if you need any info on Montgomery, Alabama.Major economic drivers to the area include Hyundai manufacturing, Maxwell & Gunter Air Force Base, major Amazon distribution, Alabama State Capitol, Alfa Insurance, Kinpak, H2 Pharma, Dollar General transport/logistics, Dow Chemical, and Conner Industries to name a few.

There has been a lot of companies building manufacturing plants to the state.

Lubbock is also highly diversified being the hub for the area from Amarillo to Midland, Hobbs to Sweetwater for agriculture production and research (cotton, peanuts, sorghum, wheat, watermelons, and wine grape vineyards -70-80% of TX wine grape production comes from this area-), medical care and research (two top-tier facilities in Covenant and the university hospital), manufacturing, transport (major airport), and of course Texas Tech is a huge economic driver employing many thousands and bringing tons of students in with their parents money (30k+ enrollment I believe, it's enormous).