My mother is dead set on having one of these Tiny Houses one day, the problem is that in most places there are antiquated minimum sizes for houses that are like three times the size of the average tiny house. She thinks she could get by in one about the size of a hard side camper and believes a mid sized storage barn is just about right. Personally I believe Straw Bale homes are a better alternative.
They are really neat but can be costly as in more than a traditional home structure if you want someone else to build them from what I've read. Of course if you are willing to learn how to construct it and do it yourself with friends or family, it's still going to be more than a tiny house, IMO. Basically you build a base and structure outline of a house and build it form straw.