I too, was going to use two 20 ft containers on a remote propriety to store my tractor and trailer so I don't have to constantly move it back and forth. I was going to set them appart, the build a roof and enclose the entire thing in the future. However, after pricing a single 20 ft container, I found out that it went from $800 each, 2 or 3 years ago, to $2700 and I needed two of those. Plus, they are just not available right now.
I had the pad ready for the containers to be dropped off, then started getting some quotes on some materials for a metal building and quickly figured out I can build a 34 ft by 20 ft metal building for somewhere around $2500. Doing this way, will also give me a lot more useable space.