Then there is the insurance factors. 

I have personally been raked over the coals on some south side properties with squatters because I wasn't prepared for the time it would take to stabalize the building.

I'm looking into the Credit Stacking program that Jack McColl runs. Looking for any reviews from previous students. 
It's a program that helps/teaches you how to access business credit to fund your business endeavors...

Likely it's that they legally have to have a physical address and as they meet clients at clients home, have them pick out roofing in a catalog and have it delivered directly to the client, there's no need for a physical building.

I have bought and sold six homes, had one beautiful flip, and kept one duplex that was a BRRR score and currently building two more duplexes with the opportunity for one more that is build ready.  

I'm considering purchasing a commercial office building that has 4 suites. 

This way you have a local physical bank for checks and other bank services, while you start building a relationship with a potential lender.

There are a number of great new construction builds around Philadelphia, and I'd like to reach out to the builders.

You have a very short window to build trust and show your credibility to a seller, the handwritten letters do neither of those things.

You will cut your cost of living down, and build equity at the same time.