It's possible to consider a single-family investment, but even then, it would be quite tight accounting for the down payment, closing costs, insurance, etc.

We're working on figuring out the local regulations for ADUs here which are a bit more confusing as it's already a duplex and not just a single family.

I disagree, I had a time when my name and the name on the insurance didn't match and the lender was all over it, regardless of the on-time payments.Your best bet is to refi into a commercial loan that allows the LLC (if you've already purchased the property), or close directly with a commercial loan / DSCR loan.

Sorry, but I've never heard a single note investor (any investor?)

It consists of an 8 unit apartment building being sold with a single family home next door to it, each on their own parcel.

Every single step of the process was mismanaged and it all felt very amature.

I bet Baby Shark would be an especially annoying song. 

New systems from Arrow Lift allow you to jack a house up in a single day, but I have not seen many contractors in the area that use them yet.

Extremely difficult to pass and I bet you didn't know that you had to get it reinspected again in three years.

If you can buy a duplex, it will cost less than buying two single family homes in the long run.