I only bought the aviary wire and hinges -all wood came from skips/freecycle. An old shed provided much of the external boards, an old pub table provided timbers for the roosts and an old desk became my feeder.
My build here:
https://www.backyardchickens.com/forum/viewtopic.php?id=52779
Feeder:
My build here:
https://www.backyardchickens.com/forum/viewtopic.php?id=52779
Feeder: