The housing being built in Portland over the past handful of years is of a specific type and a certain price range. I regularly check the rental rates for units in these new complexes as they come on line and I have yet to find units that I can afford.
Portland is very lax with it's high density zoning, or strict depending on how you look at it. They promoted high density housing by disincentivizing alternative zoning types (making it extremely difficult to find non retail commercial spaces).
The lack of rent control combined with the proliferation of high-end retail + housing spaces contributes to housing as an investment opportunity which in turn makes low end rent unstable and rare. This past year over half of the renters on my block were kicked out of their homes when owner decided to sell.
Sure, there's a glut of $1,500 studios and one bedroom units available, but there's a real lack of rooms or units below $1,000.