In my case, I have residential rentals in one LLC, commercial properties in another, self-storage in a third, and my real estate company operates in a fourth.

I am a CT based investor, flipper and property management company owner.  

Utilize any hospitals and insurance companies that are willing to take your call.

My company currently manages 15 properties, with 20+ leads in the pipeline, and we’re expecting to double our portfolio this year.

You will get killed on the C and D properties which are usually the majority of most properties handled by a metro PM company. 

Water meter-water company.  

Airbnb is a company so the only way to buy one would be to own stock in the company. 

Here's an article with things to consider when selecting a cost segregation company.

There is one city where I rent some houses and almost everyone that calls ask who the PM is and say they won't rent from anyone that uses X company as their PM.  

one of my clients that has a pretty big PM company.. had a unique way of doing this.He offered 50% of the first months rent or 500.00 minimum.. he would have 4 or 5 agents at the weekly meeting handout the list of vacants .. each of them would go place a sign in the yard and first come first served.. he found that potential tenants would call the first sign if no answer they called the next one until finally someone answered.. it worked pretty awesome for him.