As others have said, "duck ducks" don't have sphincter muscles to control bodily fluids. Where they stand when it goes is where it falls. From what I've read though diapers can be very manageable. If you make your own duck food they poop less and not as stinky as they would if you just fed them crumble, and ducks as housepets don't have so many of the vices that traditional pets do like chewing, scratching, shedding, biting. As a note though, I find bathtubs in spare bathrooms make great indoor "pens" when I need a duck inside.
I guess if he won't go for a duck you could try a ferret. They can be box trained easily, are very sweet with proper attention, and very clownish, I certainly enjoy my house ferrets!