Apartment list has a tool that lets you see, for residents of any city, where tenants are searching for new apartments. It gives an indication of where people are considering moving. You can also perform a search in the other direction to get an idea of where people are coming from.
For Spokane, most inbound searches are from Seattle, as is to be expected. (48% of users looking for places to live in Spokane are currently living in Seattle.) To a lesser extent, there are inbound searches from Portland (4.0%), Fresno (3.5%), Coeur d’Alene (2.7%), San Francisco (2.3%), Dallas (2.0%), Kennewick (1.8%), and Los Angeles (1.8%).
Most popular outbound destinations from Spokane are Seattle (24.1%), Coeur d’Alene (6.5%), and Portland (4.9%).
You can see where people are coming from (or going to) using the following link:
https://www.apartmentlist.com/research/apartment-list-renter-migration-report-2022-q1