So, my wife and I moved to a 2nd floor front Chicago greystone with no greenspace but it does have faux balcony over the front entry that can only be accessed by climbing through a window. We decided that this space must be utilized as urban gardening space.
While looking around for container garden solutions, we came across the not so affordable UK "air-pot" design
that encourages better root growth than traditional container gardening. Intrigued and still wanting an affordable solution, milk crates came to mind with some sort of liner. Milk Crates seem to be laying around all over the place until you actually start searching for them. Fortunately, we found an inside connection to "borrow" them from for the growing season.
To stay true to the "air-pot" concept we needed the liner to be breathable; landscaping fabric was the obvious choice. A $10 roll of landscaping fabric commonly comes in a 3' x 50' roll which is enough to make 24 milk crate liners. How's that for affordable?