Often advocacy groups or municipalities will perform counts on specific days each year.
So while one does not need to say "literally" in that sentence (it wasn't figurative, after all), it is possible to say "zero homeless folks" as there may be data backing the statement up.
Yes- I live in a pretty affluent Los Angeles suburb and we recently just hit "functional zero" street homelessness.
"To achieve Functional Zero, the number of individuals placed in interim or permanent housing must be greater than the number of individuals who become homeless over a six-month period, and the homeless population, as a whole, must have a median duration on the streets of less than 90 days."
The data is gathered by the city as well as local nonprofits.