Have you thought about building a granny flat? Lowe’s and other builders have have been marketing a pre-fab house called the Katrina House, named for the post-Katrina survivor’s housing needs. They are small houses starting I think at about 1500 square feet, everything included (bath/kitchen/living and sleeping rooms or areas). They send you all the materials, you obtain a contracter that builds and permits it, then you’re done.
It’s probably less risky doing this on your own property than venturing out into this collapsing market.