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 was interested in commercial and investment property, so joined a mid size commercial brokerage as a broker - associate.Most brokers/agents at that time, even more so than today, did not “specialize’, at least with very specific parameters.

Our hard money loans (commercial real estate) and the existing loans we purchase are usually brought to us by mortgage brokers.  

Make sure you review the surrounding area and watch out for the RE "doom loop" https://www.wsj.com/real-estate/commercial/doom-loop-st-loui...

You can always get funding from lenders, who usually cater to a vast majority of needs, from bridge loans to commercial financing. 

Specifically, we are enthusiastic about connecting with individuals involved in the commercial multi-family market in the St-Louis area.

I also have general liability insurance, a personal umbrella (which I don’t think will cover me as I may need a commercial umbrella).

Commercial real estate solutions for developers, home builders.

Again unless its from a Heloc or cash out refinance from another property.If you do not have a commercial loan as of yet and do not own multiple rentals you are not getting approved for a $3M commercial loan. 

What I would really like is to meet a local agent or broker who deals primarily with RE investors, commercial or resi, and just spend a day shadowing you, seeing what the job involves, and learning.