Here are two grandmothers building a house from an old trailer and papercrete on a sloping lot. I've seen trailers and modular houses on craigslist for free, so you would only have the cost of hauling it to your site. But then you would have the basic plumbing and electricity already installed. That's not a bad idea. You could live in it while you're building the outer shell. Just cover up that awful tinny trailer look. I think I would still want to do slipform stone walls and maybe build the masonry fireplace into the hill.
