My wife and I live in a small apartment with a parking lot for a back yard. There's not much room for an interest in gardening, but with a little effort and a free pallet, I made this two level planter box that yielded some pretty tasty sugar snap peas last fall.
One plus to having a large dumpster in your back yard is the occasional free supply of woodworking materials. Using a picture off of google for inspiration, I created two boxes and a simple frame using the free pallet wood. I didn't bother to paint or finish it as it wasn't built to last (hopefully we aren't in the apartment forever!) and the wood was free anyway, so I was keeping this a $0 build.