The buyer hired a law office and sent me a demand letter with a 60 day response required.

Just show up at their office,  in person, unannounced and introduce yourself--say you want to talk about real estate.Be polite and nice and I can't think of why anyone would be so rude as to blow you off...

The residential units should cover the basic expenses leaving the office space downstairs as my upside.  

Call your city zoning office and ask them.

Charlotte Metro), or find a loan officer/broker for it.I started the application for a credit union and it had asked me how much of a loan I would like, not sure because I haven't found the property (yet).

If it's not too late, I would get a Police Report.

Not saying it's  a scam, but there are plenty of loan officers that charge no fee to hassle with that mess.

It definitely will be more demanding than working a limited position in an office (certainly to start).What I really want to find is someone who might be able to offer some advice or even work to help my transition from "processor for someone else" to "Mortgage Broker for myself."

To the left of the home the property has already been converted to a business offices (although it looks just like a home on the outside).

Call the police and have him charged.