Portland multifamily has been booming in recent years, but it does not have the earmarks of unsustainable growth. Instead, there are signs of a more modest slowdown, especially in recent growth.

"Unless there's a black swan event, Portland should have sustainable growth," Investors Management Group Vice President Steve Morris said. "But due to regulations and population growth, I believe we’ll revert to pre-2013 rent growth of 3% to 5% per year levels."

Owners will have to watch expenses closely, mainly water/sewer and maintenance, because those will grow regardless of how fast or slow rent increases, Morris said.

"The other cost will be loan rates. Last year, I underwrote at 4% and now am writing at 4.75%. Cap rates will track loan rates — both will go in the same direction — which will affect pricing," he said.

There is some risk of too much high-end product in Portland, but mostly that means the market will need more time to absorb it, rather than the challenges that come with overbuilding.

"Assuming high-end means more than $2,500 per month for a two-bedroom unit, right now we’ll need time for absorption," Morris said.

The majority of new construction has been on the high end and close in, or in Portland's tech corridor.

"There are concessions being offered at the high end of the market now," Morris said. "Unlike Seattle, most job growth isn’t in the over-$90K-a-year category."

Portland's employment dynamic has not affected existing properties, especially in good locations, Morris said.

"I don’t anticipate it will. On the other hand, if you go to the other end, low-income housing rents will probably go up faster."