Also, the cabin does have a main room and a kitchen. We won't be able to use the detached structure exemption on the cabin since it is equipped to be used as a residence in the future, correct? But can use it on the barn/shed if not used for business/agricultural purposes?
What are the buildings being used for? Personal storage?
If only the cabin is in the flood zone and the main house/barns/sheds are not, can you request a split determination from your flood cert provider placing the cabin on its own cert? Just a thought.