We built the garden coop (plans purchased online) and it works well, despite the house being off the ground.
I was a little weary of how the ducks would take to the ramp, but within a week they were going up on their own at night.
I think it's probably too small for more than 5 adult ducks, but I like that the extra run area that having the hen house raised affords.
I just mention it because it was remarkably easy. I looked at a whole bunch but really liked the size of the garden coop. Figured I'd try my hand at building it.