[philwelch]

You’re both sort of right.

The visible homeless—the vagrants you see in tent cities under the freeway or harassing pedestrians—are more likely to have drug addictions or other mental illnesses. And the more mentally ill they are, the more visible they become since they end up committing crimes and making a nuisance of themselves. If you’re mainly concerned about the externalities of homelessness—e.g. needles and human feces on the street, crime, harassment, etc—then you’d be well served addressing this problem in particular.

If you define “homeless” by people not having consistent housing, there is a much larger population of those people. Maybe they’re sleeping on a buddy’s couch, or they find a kind stranger to take them in, or they get by via stealth camping. On the margin, expanding public housing or making housing more affordable would help these people. But it wouldn’t do much about the more visible and troublesome ones.