Par4QC They look nice. In pictures. But keep in mind they are very narrow, esp. after putting in insulation and walls. A 1960 mobile home...'trailer' is wider.
I have seen a lot of these built on various shows on TV. They are indeed very unique but most of them spending a lot more than just buying a nicely equipped camper with slideouts or a mobile home. I think some factory build cabins that are delivered to your site are a better buy as well.