As more and more people get concerned about the cost of housing, or the cost to the environment of making/maintaining housing, some people have honestly started to think smaller is better.
Here is an example of how you can pack a lot of luxury into a small space –
Personally, though, I’d rather go underground. If your home has at least 10 feet of earth on all sides, you’re going to have the lowest carbon footprint measurable, and if it is all electric and powered with solar/wind, you’ll generate more electricity than you need. Seriously. Pour it back into the grid, and you’ll make money off of living that way.
Vernon Pope 
I agree. Underground homes are awesome. I would love to at least have a basement, but the ground where I am buying is apparently almost solid rock not far down. Makes well drilling snd trying to put in a septic tank really expensive. Can’t imagine how much an underground house would be, or even just a basement!
You don’t have to dig to make an underground house. Just prep the outsides like you normally would for a fully underground construction, then pack the dirt around and over it. You’ll get the same insulation values as if it was built underground, and probably quite a lot cheaper.
I think it would be really cool to have a house like this, but we would need to seriously downsize everything in order to do it. I guess with an underground home, we would not necessarily need to downsize if it were big enough, but where do we find someone to build it?
I don’t think this is practical for more than a single person. But, that is only MY OPINION.