I've only visited the Seattle area once, and it was lovely except for all homeless people and the smell of pot which permeated the air in all places at all hours.  I looked up the the average rent in Redmond, which is  $2,400 a month, and just for fun, I went to an apartment finder site, entered an income of $42,000, and discovered I was limited to $1,400 a month for rent which isn't too bad.  I was unable to find anything in Redmond I could afford on that salary, but I found several options in Seattle and a few other areas with the lowest being about $1,000.  So it seems doable to live in Seattle to me on that salary.  I didn't take a close look at how nice those apartments were though.