Before investing in the space verify that you can maintain less than 50%RH with dehumidification during the extreme wet weather when your a/c is not running. Get a good %RH meter from Radio Shack or Wal-Mart. You need a powerful dehumidifier like a 90-100 pint unit that operates at lower temeratures. Check Energy Star web site for a listing. http://www.energystar.gov/ia/products/prod_lists/dehumid_prod_list.xls
Maintaining <50%RH allows carpeting use on concrete with fear of mold growth. If flooding does occur you have a couple days to dry before mold will be problem.