You can still sometimes see groups of young (teen-ish to 20-ish) homeless people in Harvard Square, including with dogs sometimes, though not as much as you used to. There at least used to be a mobile health clinic that would visit "The Pit" area around the Harvard Square subway station, where young homeless kids would congregate. (Also, non-homeless kids, such as from affluent suburbs, hanging out and being cool/punk/real with the homeless. But some of them actually are homeless, maybe escaping from rough family situations.) I understand there recently is/was a dotcom-y charitable homeless shelter in Harvard Square (unless it already disappeared; sometimes projects fail, or are career steps).

Cambridge, Boston, and Massaschusetts are wealthy, and good about social programs and safety nets for the poor, by overall US standards. But the winters get cold, so a lot of homeless who are able might go to the SF Bay Area.