The latest: Sis & her husband had a floor plan created to basically build a finished "addition" to their barn (call it phase 2, with the barn itself being phase 1), and phase 3 would be to eventually finish much of the inside of the barn to complete the house. The plans were great, sis loved them, aaaand the bank told them to get bent.
They can get a loan to finish some of the inside of the existing barn, so that's what they're going to try and do. She loved the floor plan so this complicates things a bit since they're basically going backwards (the master bed/bath is part of the attachment, not barn build-out). They're trying to figure it out now.
Moral of the story: If you want a barndominium, you better plan for everything up front with input from the bank, and you better be cash rich because you're not going to be able to finance 80% of the build cost like you can with a regular house.