Portland might be a growth market for apartments, but it faces a challenge common to a lot of places that can be summed up in one word: affordability.

"The most serious challenge facing the Portland multifamily market in the coming years is the need for significantly more housing supply for people at the lowest end of the income spectrum," Home Forward Executive Director Michael Buonocore said.

It is difficult for projects to be financially viable without ongoing subsidy, which is primarily, but not exclusively, provided through the federal government.

"We will need more investment [through] HUD, and/or dedicated local revenue streams that support the lowest income households, or we can’t make meaningful progress to end homelessness," Buonocore said.

Williams & Dame Chairman Homer Williams agrees with that assessment.

"Affordable housing will be the defining issue in all local and state races. If we cannot solve it, we will need to redefine what acceptable affordable housing is," he said.

Other challenges face Portland multifamily as well.

"From my perspective, the biggest challenge for the Portland apartment market over the next few years will be the surge in medium-term supply and the cost to deliver quality urban housing," Green Light Development founder Mark Desbrow said.

"This will most likely result in compressed yields to investors over the next three years, until the supply spike burns off. This will be good for renters over this period of time as the scale finally tips and Portland becomes more of a renter’s market."

Construction costs are also problematic.

"Portland's multifamily market faces several challenges that will impact the availability of housing in the immediate future and more long term," PHK Development President Patrick Kessi said.

"New construction costs continue to increase rapidly, while the city approval processes often turn into lengthy efforts. And the city's new inclusionary zoning requirements will compound both of those issues, as we all strive to increase housing availability in Portland."

Find out more about the Portland apartment market at Bisnow's Portland Multifamily Investment & Development Summit Feb. 22 at The Nines. Buonocore, Williams, Desbrow and Kessi will all be speakers at the event.