The SMH has an article today about modular housing for the homeless, with the modules built off site in factories and half the cost of building them compared to onsite construction. The modules appear to be about as big as a 20/40 foot shipping container, which would suit transport.
Some years ago, a TV featured a capsule hotel in Tokyo, Japan. The capsules were quite small, you could not stand up in one. They contained basic bedding, washing and storage, with baths and toilets perhaps located elsewhere.
Not bad ideas, really.