I was fortunate enough to procure a fully functional caravan to use as a duck coop. The caravan is about 5 meters long and 1,5 m wide. We drove it to its location, and presto! Complete duck house just like that!
It needed a roof, and an outside pen. As winter came, I realized the need for wind and snow stopper, so I added some strong plastic to the netting walls.
The caravan has two natural openings; the regular door and the little door for the propane tank, that coincidentally is exactly the size of a duck. That made it easy to part both the inside and out in two with netting and create two separate pens. For those birds who just won't get along, or to separate different drakes for mating.
And now the inside. As I said, the caravan was fully functional when I got it, complete with tables, sitting arrangements, shelves and a fridge. The latter is not in use, but both the table and the seats are still there for the ducks' use. I cover the seating area with paper feed bags for easy cleaning, and have a thin layer of straw on the floor that I change out every week so those messy ducks don't get the floor wet.
The table is their favorite spot.
I cut holes in some of the interior to create nice nesting boxes for them.
It's been in use for 2 years now, and the birds love it. So much so that the chickens occasionally come over for a visit.