One of my Uncles lived the type of life you describe. He drifted from town to town picking up enough work to stay fed and occasionally housed. He showed up at our house every year or so. Once he showed me his notebook, it had lists of food kitchens, shelters aid and veterans centers in dozens cities. Even when my Dad set him up with a furnished apartment he continued to live on the street. For him and his reasons, it was the life he chose.