The city of Seattle has 0 power to force other municipalities to build housing.
Any attempts by Seattle to build shelters and low income housing projects outside of the city limits would be swiftly shut down, assuming those attempts could even get started.
Unfortunately Seattle has to pay the burden of the entire region. While some cities, such a Bellevue, are helping out, other cities around here have no real desire, or motivation, to start paying money in, and voters in those other cities would likely make that clear the second their elected officials started spending tax dollars.
we have instances of cities facing outcry from residents for simply building homeless shelters within their own limits[0][1]. I imagine the outcry for a city "shipping out" their homeless to a shelter outside their bounds would be even worse.
[0]: https://www.theguardian.com/us-news/2019/mar/28/san-francisc...
[1]: https://www.ocregister.com/2019/04/02/huntington-beach-scrat...
It would cost billions but it already costs billions nationally to care for the homeless. With lower wages and land values you'd have large cost savings and that's before economies of scale.
Let the addiction specialists and mental health professionals set the rules here. They would be limited by the constitution but would be able to enact laws for this very specific segment of the population. A low trust society encased within a high trust society.
At that point cities would be free to enact laws to the effect of "get help in the complex or go to prison" when they catch the homeless committing crime. Homeless no longer are a blight to the cities and the homeless get the best help we can offer.
Relocation should be behavior based (so not "vagrancy", which is a BS charge, but actual public misconduct or documented threat of self-harm). X strikes and you're relocated unless you can fund an appropriate bond.
The rest of the state is probably a healthier place to heal in any event... easier to control access to drugs and alcohol and limit the violence from street predators. The street isn't a very supportive environment....
They also have 0 power in forcing people from the region not to come to the city to become homeless. It is a regional problem, Seattle can only do so much by itself, as you say.
Arguably the coastal cities pay a disproportionate share of social welfare program costs for the entire nation.
Perverse incentives, small towns can not invest in the future, and just outsource the consequences to larger municipalities.
However, the chronically homeless, at ~20% of the population, take up over 50% of the budget. They aren't able to live independently, regardless of any reasonable cost of living. They're also the most visible group.
We should keep in mind that the solutions for the two are vastly different.
This seems pretty good: http://www.evidenceonhomelessness.com/wp-content/uploads/201...
Either they wind up back where they started because East Nowhere, North Dakota wants them gone too, or you wind up with concentrations of homeless people in an area with minimal tax base and horrific conditions as a result.
If you've got no prospect of sustaining yourself in a specific city because it requires competence beyond your capacity, you've got no business in that city. We should aim to help put people in circumstances where they can thrive sustainably on their own.
None of this should be compulsory. I'm only suggesting that the support being offered for free should be focused on putting people in circumstances that match each individual and that cost the least amount to those providing the resources.
If rent gets so expensive that plumbers can't afford to live there, then some plumbers will just start coming in from some cheaper area and charge customers probably an increased fee based on the trouble of getting into the city.
There are alternatives for everything with their own price. Even if it is horrific like "die of rabies instead of getting vaccinated after being bit".
If availability of workforce in a broader area is high but in city housing they afford is low either they need to be paid more or traffic and commute time will increase and make the job less desirable which may affect skill level and harm labor availability. Underserving is technically also an option but there will be knock on effects - if the schools are bad then parents will be more likely to relocate.
Not all parents. Only the intelligent, cultured, and high income ones.