Plus, although you guys want things to be temporary/portable....
You said yourself that you will be living in it while you build your homestead. That could take six months to four years! You need to be able to be comfortable and not risking danger from some thrown together thing.
And keep in mind, anything you build, you can take apart! Although cement is pretty hard to tear down I don't think Cob
would be so hard to pull down, but then again I have never worked with it before.
And, yes why sand? Is it available in large quantities on your property?