There is more than 1 way to build a chicken coop. Depending on whether or not you live on a farm or in an urban region, you will require a chicken house plan that suits your requirements. This post outlines some different designs.
If you are not fussed with the aesthetics of your chicken house, and just need a safe, secure place to home your birds, a basic “box” design will suffice. It is really unattractive, and all you need to have is some low-cost wooden framing and a weatherproof material for the roof and walls. If you live on a farm you will probably already have most of the “junk” you want. You don’t even require to build appropriate nests, and can use cardboard boxes if you really want to cut expenses.