Minor spoilers ahead
(unreal estate copyright
Transients are people who live in their houses, which are powered by Mobile Reality Engines. In that sense, they are somewhat homeless.
True, they have a home, but their home has no home. They move from reality to reality, negotiating docking fees and passport processes, and can rarely stay in one place for a long period of time without running out of cash in the process. To be a transient is to lead a life of excitement, adventure, and near poverty if you're not very good at it.
Some have found prosperity as transients, such as traders and merchants who keep storage, sales and exporting all 'in-house', so to speak. Other businesses which work best when they come to you such as non-corporate owned personal taxis and delivery services thrive.
Still, there's a negative stigma attached to transients, since they're perpetual outsiders no matter where they go. Some realities such as Grunwald have a closed door policy to transients and prefer to deal with them as little as possible.