First question.....why block?
I went to jr. high and high school in Brevard Co. Lived in Melbourne Beach, Eau Gallie, Indialantic, Seacoast Shores etc. I know block is sold as the perfect hurricane solution there, but it is expensive because of the labor. Have you priced all the alternatives?
Metal building, Wood frame construction, Metal frame construction and combinations?
Does your budget mean a turnkey job with insulation, all interior finishes and storage and A/C? What parts of the work do you want to do yourself?
What contractors do you have lined up already?
Why a 12/12 pitch roof? You only need that up north for snow removal. You could go flat roof there. You could use block and either steel or wood joists. What wall height inside? Is 24x24 the max you are allowed? Have you checked zoning and easements etc? What is your lot layout and what does the house look like? What style? We need a lot more info and photos.
Bill
Arch. Designer in Detroit