Sharon out of the areas of Fort Walton Beach, Niceville, Navarre and Crestview, I found 17 properties with a home that's at least 1700 sqft and at least 3 acres under $350k. (and most were under $300k). I think one actually had 25 acres on it. A few may bit a bit of a drive, so if you are still Active Duty, (going from the USAA prequal) you may want to consider which base you will be, to determine what kind of drive you might want to make daily. You can take a look here: The following are the links to the selected listings.
If I can answer any additional questions for you, don't hesitate to ask.
Karen Butler, Realtor
Coldwell Banker United Realtors
Military Relocation Specialist