Born Under A Wandering Star
For some reason, thinking of SF novels about the hobo life, I forgot all about James Blish's Cities In Flight series, which describes an interstellar civilisation in which cities use antigravity motors to wrench themselves free from Earth and soar through the Galaxy, looking for work. Which was pretty dumb of me, especially as I provided a blurb for the SF Masterworks edition: 'An outrageous imaginative coup . . . Crammed with high adventure yet illuminated by a searching intelligence, this four-part epic completely reinvented the traditions of space opera'.