If it's your first deal and you don't feel confident in your abilities, I'd recommend paying an attorney to review the closing docs. 

Short of actually trying to navigate these waterways, is there a way to determine how navigable specific waterways (bayous, creeks, rivers) are?

Investing in a PRO membership unlocks more abilities to connect, but you shouldn't have a problem finding local help either way.Good luck getting that first property!

The income drives BOTH the ability to get a 'normal mortgage' AND having that down payment. 

I recommend finding a strategy that fits your desires, goals, and abilities and then learn about that strategy, your target market, and how to build your team.

Nothing about this is turnkey and I would serious question their ability to manage or rehab a property

My question is... what specific part of the analysis should I be focusing on to determine if it’s a good deal.

Some things to consider now, before you actually start investing, is to determine what type of investing you think you'd want to do (Rental Property vs House-hack, Fix & Flip, vs Airbnb, vs Wholesaling).

This is one of many threads going on right now expressing everybody's dislike for the new forum layouts and loss of user ability.

You need to determine what is important to you and focus on what you are willing to do to get you to your dream.