Low closing costs is better for the vast majority of borrowers.

But, I'm not a licensed appraiser, the OP is not a licensed appraiser, and I'm guessing that the vast majority of the investors reading this are not licensed appraisers. 

A quick letter thank them for paying on time and taking care of the properties in addition to letting them know what is going on would be sufficient.

Another thing to consider is FHA self sufficiency test for 3-4 units.

In the mean time, a building like that will burn cash fast, so if your reserves are not sufficient, that could prove detrimental.

You have sufficient equity to pull out a strong down payment while still having your existing property provide you with a good amount of positive cash flow.  

I doubt a 100A panel will be sufficient to power the main house and an ADU.

I hate to see people lose their hard earned money and investment when you are not sufficiently capitalized is the easiest way to lose yours. 

Is this sufficient to reap the S-corp benefits at the end of the tax year?

Don't forget about the FHA Stress Test (self sufficiency) required on 3-4 unit properties and the cool benefit that you can use 75% of the market rent for the other 3 units as income if you need it to help qualify for the mortgage.