May I please offer just a word of caution? Getting into ducks is more than many people think. Of course the "housing" issue is important. And there is a lot of advice here about that. Free rangers or not, you will have to provide food. I always feel that good all around food is Purina Flock Raiser (mostly corn crumbles).
As hardy as ducks are, you will still need to be on the lookout for illness and infirmity. And the list of things you need to do for them tends to grow, the longer you keep them.
Maybe it's just me, but I feel it's only fair to make you aware that ducks honestly DO need some basic care from you, so please be aware, before you decide to be responsible.
Having said that, I can tell you that my ducks have provided me no end of pleasure. They add a pastoral feeling to my home, and I would not trade that for anything.
Good luck, and stay close to this forum! There are people who have encountered everything possible with ducks. All you have to do is read.