mochicken, I agree with dickhorstman.
It depends on how much you can put into keeping the little ones warm enough, dry enough, etc., which can be a challenge. I brooded eleven runner babies that arrived a month early, so they were in the house for three months - it was simply too cold in the outdoor duckhouse for them. It was a late spring, too. sheesh.
It was a blast, actually, and the house didn't smell - I was changing the brooder bedding and water three, sometimes five times a day. It is practially all that I did that late winter into early spring - charwoman for ducklings.
If you really love devoting yourself to an intense experience, by all means, go for it!
For their sakes, though, think long and hard. Do a search of Duck Forum topics like "duckling mess water" - we have posted dozens of good ideas for managing water with brooding ducklings. So often, I see topics to the effect of, "They were so cute but mercy they have quadrupled in size and they poop like there's no tomorrow and I can't keep up and it stinks and WHEN CAN I GET THEM OUT OF HERE???"
It's just what ducklings do. The benefit, of course, is the unsurpassed charm and often goofiness that wraps us around their little wing feathers.
So. What kind of space to you have and what's your planned brooder setup?