Muscovies are my favorite ducks. However, they can fly very well. If you want them to stay in your city yard you will have to clip the primary - and maybe secondary - flight feathers [NOT pinioning]. Ask your vet how to do this or go to a pet store that specializes in parrots.
Also, there are people who keep ducks and geese as pets in the house. You can actually get harnesses with a place for diaper inserts. Pretty frou-frou! LOL
But if you just want a couple of nice birds to eat your weeds and bugs AND give you eggs, then go with female banty chickens or female muscovy ducks. Put them up at night or whenever you are away from home in a secured pen safe from weather and prying eyes. If you don't mind having them indoors you can turn an extra bathtub into a night time safe place for them. We had a jacuzzi that came with our house that we never used but I raised many baby ducks and geese in it!
Just make sure that whenever they are outside they are safe from wandering dogs and cats.