I found an old airport luggage wagon on Craigslist for $200 and decided to buy it and turn it into a mobile chicken tractor. I have a 2-acre field that I can move it around on (though the chickens roam on my entire 5-acre property). I think I have about $450 into the project, as the side panels were a bit pricey, as well as a new paint job and hardware (latches, handles, etc). The trailer is nearly 1,700lbs, but it pulls easily with my garden tractor. I designed it so one side opens up completely (2 doors) to collect eggs and periodically clean it out. All I do is pull it up to my garden, open the doors, and scrap out the bedding onto the garden bed. The other side has a couple of vents and a pop door. In the Spring I will be mounting a 55 gallon barrel on the top (laid on its side) and will install a bell waterer inside.