First of all thanks for your Service to our Country.
An RV lifestyle would be much easier. You should check out Sigsbee and Trumbo Military campgrounds in Key West. I think it's something like $21 / night. You may have to move every two weeks but it is about the cheapest housing down there. Last time I was down there my bus driver was retired military living on one of those campgrounds. You can still get in a lot of boating at the same time without needing a boat big enough to live on. Best of luck.