If they are offering unheard of rates or LTV, then all their competitors would be out of business. 

I know a teacher who has a house painting business he runs on the side/ in the summer.

If you have a good business plan for the next property it could make a LOT of sense. 

STR is a hospitality business.

I often do site visits to the property and then design/draw the hvac/plumbing systems for the building.From what I gather below the following would all fall under "real property trades":"The statute lists 11 types of real property trades or businesses: real property development, redevelopment, construction, reconstruction, acquisition, conversion, rental, operation, "I believe that my line of work can be classified under "real property development", "construction", "conversion".

If you are focusing on volume, you might have to adapt your ROI to be able to acquire more properties and keep your people busy.

That will be a huge benefit as dealing with contractors is one of the hardest parts of the business in my opinion.

Yes I am familiar with all that you mentioned as I have several LLC's for my business and investment properties. 

I earn much higher returns than I ever did as a rental investor, and don't have to lift a finger after the initial vetting discussion.That said, some investors really do enjoy building a side hustle business around real estate.

You might also meet someone that could be a potential business partner.