There are markets that are seeing massive growth, which therefore you could call "a better market", however at the end of the day the grass is greenest where you water it.I'd recommend building those broker relationships 1-by-1 or invest passively with an experienced sponsor team to get access to other markets outside of your area.  

What are you going to do if they move everything out and then you find the massive water damage, wrecked floors, and damaged walls?

Speaking purely from the standpoint of you qualifying for another mortgage, you at least need to charge enough to reduce your debt burden and get your DTI ratio below say 50%. 

Which looks like a water damage. 

Then ask what it's worth for them.There's no time for them to accrue any meaningful amount in that time span if charging purely interest. 

Water and sewer are expensive in Portland as well and I pay that as the landlord. 

I would factor in a certain % each month for capital expenditures, such as a new hot water tank, furnace, etc. 

Water heater, roof, HVAC, paint, flooring, siding, windows, etc.

Otherwise, you could look into non-conventional loan options (outside of Fannie/Freddie) that allow for less than 20%, such as local credit unions.As for your numbers, you're missing a few important components; the big items would be maintenance, CapEx, and utilities (water/sewer/trash) for a 4-plex.

This will really only be economical if there is municipal water/sewer right out front the park that you can connect to.