I agree moleskins, geese are the most economical when it comes to weighing it up but they are definitely not for everyone. Pigs are pricey to keep, but our neighbour at the time was the village butcher.
Our very first hens years ago went straight up into our low fruit trees as soon as we let them out which surprised us no end and we kind of forced a house upon them. When we moved to our present place we inherited around 20 hens, all roosting in trees all year round, they looked like huge Christmas puddings up in the trees at evening time. We got used to it and saw how easy it was, no shutting the house at night, opening in the morning. We didn't have any cleaning out to do and there were no mite problems to deal with. We did try putting them in a house when the snow came but they obviously hated it and were very stressed so we gave up and they happily flapped their way down with frosty and snowy backs in winter - I would give them rice crispies with warm milk to 'defrost' them which they were most grateful for. We gave lots of them away to friends who all kept them the same way. We now just have 6 as that's enough for us at present but they are very old now and we will get some new stock next year I think.
They won't roost in coniferous trees, too dense, but nice loose knit trees helped by a ladder made from a plank of wood with quite close regular rungs suits well - you can always pick up your hens and show them how to get up, they get the message pretty quickly - they will most likely look for a high place to roost at evening time anyway. Hen houses are pricey and I would think twice before parting with cash for them, perhaps advertise for a kids timber wendy house and adapt it - would work just as well. There is a website called
www.freecycle.org where people advertise stuff for you to have free so its recycled, someone may have one for free. A traditional dog kennel adapted (add legs and roosting bars easy peasy) would be fine too.