In its early phase, as the church was starting to get established in Europe, there was a group of itinerant people called the gyrovagues. They were gyrating and roaming monks without any affiliation to any institution. Theirs was a free-lance (and ambulatory) variety of monasticism, and their order was sustainable as the members lived off begging and from the good graces of townsmen who took interest in them. It is a weak form of sustainability, as one can hardly call sustainable a group of a people with vows of celibacy: they cannot grow organically and would need continuous enrollment. But their members managed to survive thanks to help from the population, which provided them with food and temporary shelter.

Source: How To Legally Own Another Person – Evonomics