Eviction involving a SFR turned into a duplex..

[Bob Jones]

I am a property manager around the Seattle area and one of the single family residences has been a duplex for some time. Having rented both units out it has not been an issue until the issue of non payment from the downstairs unit has come up. The whole place has one address. one electrical box etc but I am curious if eviction of the lower unit is possible without the removal of the upstairs renters also. I know evicting specific peoples isn't allowed and addresses have to legally be split up (compared with just writing 1/2 etc on the mailboxes). so I am curious is it a possibility and if so/not what are the general steps/guidelines to do so. Thanks in advance!