The homeless, despicable as they are to many of us, are a group of citizens who live sustainably in an urban setting. Since charities do not provide for the homeless anywhere near what they need to subsist the homeless adapt and live admirably among us. They eat out of garbage cans, which recycles our wasted excess. They wear minimal clothing and their bodies learn to adjust to temperature extremes. They live without plumbing, water or electricity. They get by without an income or life, medical, dental or eye insurance. They travel long distances on foot or by thumb, on trains or rideshare. They live outside year round watching the seasons change, seeing the moon wax and wane, noticing the perseid showers, the comets, the strange and unusual, the warming climate, the northern lights deeper south this year and a host of natural phenomena invisible to city dwellers and house-rats. They survive on rice or bread, without coffee or chocolate, they consider a cigarette a luxury, and luxury an extravagance. They just as often travel with animal friends that are equally unwelcome in the civilized world or feed the birds, name the feral cats, notice the pigeons. They work odd jobs, collect recycling or panhandle for just the bare minimum. They own almost nothing because that is what they can carry.
They camp out on public land to remind us that public land isn't really public, they light fires to remind us that the oldest way to heat ourselves is now illegal, they sleep in doorways and on sidewalks to remind us that coming and going isn't just about commerce, they squat in condemned houses to remind us that freedom isn't free and they show us that we need to remember that there is something lost when living and alive are separated into two different categories - one meaning to make money and one meaning to be in existence.
When Intentional Community is considered think about being homeless - it just means nomadic, or tribal. Sustainable means maximizing minimalizing. Minimal living is sustainable and if we are willing to pay for sustainable then we should be willing to approve of minimal. If we can admire the native ways of life we can admire the Urban Nomads and learn something about being less fastidious in order to be more intentional about waste and want. Doesn't matter how you got there, once you get grubby you are already closer to going green and being organic than you were before.