I agree with goosedragon...I use an electric net fence I got from Premier 1 and I think it was worth every penny. I use a solar energizer, which, admittedly is the most expensive option up front, but I don't need electricity to run it, ever, so I can put the fence anywhere on my property, not just near the house. We have every predator imaginable where I live and my ducks and geese spent their days all last summer and up to freezing inside the fence and were never bothered by anything. I bought the 48" high fence, but I actually wish I had gotten the slightly shorter one, as it would be lighter to move around. I priced wire fencing and anything other than poultry netting seemed like it was going to add up to plenty of money...poles, fencing, wire, gates and the time to put it all up. I can move the electric net fence to a completely new, fresh patch of grass in about an hour, or a bit more if I need to mow.
The mobility of the fence is a big thing, something you won't get with other kinds of fencing...your birds will eat the grass, and make mud holes and the poop does accumulate and you will lessen the chances of parasites and other nasty tiny visitors if you move their grazing area around. I cut way back on mowing this year because the ducks and geese ate the grass down.
I do lock everyone up at night inside a converted garden shed. It was easier and cheaper to put in a plywood floor, add a duck door/ramp and paint it than build something from scratch.
If you have to build something and want to cover it and also get a pretty big structure, have a look at the starplates and example structures that are on
www.strombergschickens.com/starplate. These are geodesic domes. Here is a picture of the one I built. It is made from 2 x 4's and bolted together. You can see that when I took this picture, I had the electric fencing set up so the birds could go from the duck house, through the duck dome and out into the fenced area. I use that set up only part of the time, since the grass gets pretty beaten down. When I move the fence farther from the dome, I just herd eveyone over there. I have used poultry netting on the "walls" (there is plenty of support for that sort of fencing on this structure) and I am going to cover the roof next spring with something more permanent. The plywood on the back walls is for the winter only, to stop the wind. I will take the plywood off in the spring.
I am not a genius carpenter, and I managed to do this nearly all by myself. My husband helped me raise the roof section. I built mine this big because I wanted to be able to walk right into it and also be able to convert it to a greenhouse if I ever wanted to. A smaller one would make a great little pen for a few birds.