"- we could build housing for the homeless from all those containers, and completely eliminate homelessness in this country, if only we had the land to put all those containers somewhere else."
Much love for my ISO containers, but the homeless problem isn't necessarily due to a lack of "homes".
If you have "land", then the ubiquitous "single wide mobile home" is usually a better choice than the "same thing in a shipping container". By the time you turn an ISO into a lodging structure (as many firms do, check the Sea Box site for great ISO container pron) they cost more than a single-wide.
Container homes are great for DIYers with a metalworking background, and they also make hip structures for the rich. They don't necessarily save much if anything in construction costs if hiring out the work, but you wouldn't know that from the many people pimping them.
If you have a place to play and the inclination, grab one or more 40' High Cubes (standard height sucks for many reasons, and since 20-footers cost so close to 40's it's usually silly to get a 20.
I just spend the day welding a splice strip between my roofs (use industrial roof coatings BTW, NOT the vile rust-promoting shit from chain stores!) and after coating the roofs (about a grand in materials) I'll be adding a man door and removing some of the walls between them. It's shop space but I'd live in an ISO home without hesitation. If I had to pay retail for everything, I'd go ICF (insulated concrete forms) with a slab floor instead.