You might check the "My coop" tab; there are lots of ideas there, and many of them give details of how they built it.
If you live in the South, or really any place that does not get heavy snow, you might look at these:
https://www.backyardchickens.com/t/163417/please-show-me-your-hot-weather-coops
Most people use treated wood for any parts that touch the ground, then whatever is cheapest for the rest. 1/4" hardware cloth or wire mesh is a great material for letting air exchange but keeping predators out. Metal roofs are easy to install and last a lifetime.
A lot of people purchase a shed and convert it, especially a wooden shed. Many others gind something that 's list.
For prices, you just have to shop locally. We do better at the local lumber yard than the big box store 25 miles away for many items. Also, check for a coop or shed at a great price on Craigs list.
If you add your location to your postbit (go to My Profile and find the location box,) it often helps when answering questions.
If you want an enclosed coop, or if you live in the north, check out the two coop links in my signature line.
Good luck!
