FWIW, many of the homeless individuals I see sleep during the day and are awake at night. During the day they can sleep/nap in public places in relative safety, while at night its a very different environment. They also tend to hang out in small groups, especially at night, that way one member of the group is always awake. I also routinely see creatively concealed hideouts in doorways and landscaping areas of very active office buildings. Addictions and mental issues aside, the chronicly homeless are very adept at surviving in the city.