Some banks require 6 months before you can lease or refinance- so you have to live there essentially as a primary residence for 6 months.

They came and replaces the meter on my personal residence one day when I was at work.

Our next purchase, a SFH, we purchased in our LLC’s name and paid $10k cash for it at a county tax auction.We also each had former primary residences that we’d turned into rental properties.

Most of the credit unions I spoke with lend at prime rate or even below prime rate if you go with a lower LTV, however to get the amount of credit I wanted I decided to borrow up to 95% LTV of my primary residence 

Assuming there was no simple typing/scrivener’s error, then making a deal with the neighbor seems like the only solution.....maybe a prescriptive easement.

When buying a primary residence, there is no limit of financed properties with many lenders, although some are still going to have overlays and limitations.On your second question yes, you can always pay your loan off with cash, or pay down your balance, and later refinance. 

We're currently working on some minor TLC on our personal residence and are going to look into using a HELOC to fund our first flip.

FHA loans for mixed use properties are absolutely available for primary residences.

Having said that, if you don't have a primary residence yet, you could look at a multi unit and get started with that.  

I think I've worked out a solution.