Welcome to the forum!
Looks like you have asked about an area where we don't have knowledgeable forum members. Mrs S and I wintered in WPB for part of 3 winters some years back. All the campsites were reserved out for the winter, but we found a mobile home park just off Southern that would rent to us monthly.
You asked about storage, perhaps a mobile home park might either have a storage area or might have a vacant mh lot that they would let you park on at a reasonable rate, since you wouldn't be using water or electric. Might be worth a shot if you come up without better options!
Bad decisions make great stories!