Hi, Cynth,
when we say "ducks," that is a BIG group!
There are many breeds, and depending on the breed, size of flock, and your management style, there could be different answers to those questions. (c:
I love my ducks so much! They are beautiful and delightful! And they have not read the books, so they don't always do what others (on the forum or in books) say that "ducks do."
There are some things they have in common though. They need warmth and a clean environment growing up. Many people are shocked, shocked I say, at how much wet mess their ducklings make. Some of that may be expectations, some may be limited space, limited time to do cleanup, learning curve about duck behavior. It also depends on how many you have.
Meat duck eggs can be eaten.
Most ducks don't have to have a pond and in fact, a pond with predators is a bad idea, IMHO.
They need water every day. They might not leave, they might get sick and die. (May sound like an exaggeration, but really, they need fresh water)
In winter they need a warm enough, dry enough, free from drafts enough place (and that is all over the map, based on what I have read here), and enough water to wash their heads in to prevent sinus and eye infections.
Any infection left untreated may become serious, as in, fatal.
I use a concrete mixing pan for them to swim in.
They need at least 25 square feet per bird if they don't have pasture (yard) to regularly explore. That is from Holderread's book.
I hope this helps.
I want people to have ducks, and to enjoy them. And I very much want the ducks to be loved and well cared for, too. If you and all of your family are okay with some level of splash and poop, that's a good start. If not, I would suggest you not cause yourself and your ducks a bunch of heartache.