If you need more ceiling height, my recommendation is to get a licensed contractor and engineer out to survey your site and see what's the best option.

Any advice on what documentation I should be asking him for (project schedule with timelines, expected bill of materials, permits, surveys, utility plans, list of all of his subcontractors for each specialty, types of insurances required, etc)?

Talk to survey companies.

Found out that there was never a plat, only survey drawings.

Eventually yes you might have to pay for a survey or appraisal and maybe a small amount for something. 

  :)  Florida did a study in 2010 and found that in the claims they surveyed, Public Adjusters got payouts 574% higher on regular claims and 747% higher on hurricane claims. 

You'll need title and survey fees.

Hey @Rene Doyle , the first step is to get an elevation survey.

This page provides the latest reported value for - United States S&P Case-Shiller Home Price Index - plus previous releases, historical high and low, short-term forecast and long-term prediction, economic calendar, survey consensus and news.

Americans are increasingly favoring renting over home ownership according to the most recently conducted Freddie Mac renter survey.