integrating homeless people in permaculture designs may be mutually beneficial. sure, you'd have to be a bit selective, but look at the homeless garden project in santa cruz
http://www.homelessgardenproject.org many people are homeless due to socioeconomic reasons outside of their control, and some by choice. many travel around the country for seasonal harvest jobs.
maybe creating a safe space for homeless people, providing them with surplus food (remember principle 2) and have them help with certain labor intensive tasks can be a good mutualism. many also have much to teach, whether they have a phd and are living on the street or are illiterate but great observers.
nomads and travellers also are the least vulnverable and most ancient communication system, something to keep in mind if interwebz and phones dont stick around
definitely not to be romanticized, definitely to be learned from - from skillz of bricolage and adaptability to just considering our own privilege.