In 2013 we bought an 8×12 galvanized greenhouse from Tractor Supply for $100; it has been worth every single penny we paid. For the past three years we have started every transplant under its green meshed plastic. This year, however, the green covering had become too weather-worn and so was tossed in the trash. The steel frame is still in perfect condition though, no rust or warping anywhere, so we decided to keep using it.
We leveled the galvanized frame and then boxed it in around the bottom with 2×6’s that we got free for hauling them from someone else’s yard. Roy has been collecting 2×4’s for some time now so we used this free lumber, too, and framed up the ends. We already had plenty of nails and screws around the house. The only thing we needed was a covering. We bought a roll of 4ml plastic from Walmart. Voila! We have a tiny greenhouse that is working perfectly for starting this year’s transplants for only 25 bucks! Now that’s a cheap greenhouse.