I am always trying to find resources that will help my clients to better understand what goes in to taking on a remodel or addition versus just going with new construction. I found this article on Home Advisor that clarified a little, but still leaves a lot of questions unanswered, and really some things were not true at all for Florida.
Click here to see the full article and plug in your address to get more accurate ideas of what you will need for an addition or renovation. In my opinion the numbers are a little low for remodels in Central Florida. It is a good jumping off point though to have questions to ask your Contractor or Designer.