You have to evaluate based on market, but there are other means of achieving forced appreciate that might make more sense. 

I currently live in Charleston and am a fishing guide by trade so I have a good base understanding of how water moves through salt marsh areas, but it'd make me feel a lot better about this purchase if I could have an expert look at it.

Based on my experience builders make a lot of mistakes during construction.

4) any Charlotte based resources that come recommended to help me structure this properly?

Always weigh the pros and cons of each option based on your financial goals and circumstances.

Sounds like prices vary based on each situation but I'm looking at $15k.  

Based on your description of the situation, you're not going to cashflow while you live there, but the question you should really ask is, will it cashflow after you move out? 

(And it seems there's at least some chance it doesn't pass at all, based on the opposition they're setting.)

Demand for short-term rentals is based on emotions, the allure of this view or that amenity or this undefined "feel" or "design" of a place.I'd love a pamphlet that says simply, "Hot tubs increase gross annual revenue by $22,000."

FYI we've changed our approach entirely and have lower fee initial entry points to avoid the challenges of long term project based arrangements so we can catch issues much sooner.