Ducks are just as easy to care for as chickens. Other that more water maintenance and providing a place to swim or at least dunk their heads. But ducks really are happy with water to swim in, so try to find a way to make that happen, even if it is just with small bins.
Ducks make a mess of their water.
I have a duck house and a chicken house. Both are hosed out each morning. I hosed out the water dish in the duck house and refill. The chicken house gets water refilled as necessary - but daily change out isn't needed.
They both eat the same food.
They both free range the same yard.
They both lay eggs in their house.
I do house mine separately.
They free range together though.