"To sum it up: There are homeless people who migrate — somewhere around 15 to 20 percent of all homeless people — but there aren’t many who migrate far beyond their home state and region. While research hasn’t definitively answered the question of how many homeless people migrate [here from outside Washington State] just to get help, we know that in King County, 3 percent said they did."
https://www.seattletimes.com/seattle-news/homeless/do-homele...