What would a fair cut of the profits be?

This has created a "shared driveway" with the neighbor making an ugly curb appeal, not to mention cutting their lot in half.

All of that is pretty cut and dry. 

I have a few commercial bank contacts, but concerned they may just cut me out of the deal.

Quote from @Anil Shah: It's unfortunate Raleigh-Durham didn't make your cut of 13 cities but Charlotte is definitely the city to choose in NC if your want the city feel.

They cut out all but the best locations and were way more cautious.

(May also cut significantly into the current cash flow on it)I know you mentioned not doing a HELOC on my primary, but wouldn't it be advantageous to have the ability to pay off the line of credit instead of be stuck in a payment that is much higher? 

If I do this, my PITI would jump up to $3,090, really cutting into any cash flow and the interest rate would jump to 8%.

Just have two small rooms to finish, grout and cut tile pieces for edges.  

The foundation was already approved, permitted and finaled years ago for a 3400 sf house, and its solid and I won't be building directly on the overhang edge; but rather back away from the edge a few feet to prevent any load issues all the weight will be on the longer sides of the existing footing.