Hi, Ryan -
I'm a Seattle
native (yeah, there are still a few of us here), and have been looking for rural property to homestead for the last 8 years, intensively for the last 18 months. I started looking in Skagit and Whatcom counties, because I like Bellingham's cultural vibe a lot, but land in those counties is rapidly escalating in price - we needed something unimproved for under $35K, or improved for no more than $80K for 2.5+ acres. No dice.
Heading south; Snohomish county has some cool properties east of Everett, like you say, Granite Falls and Arlington/Darrington spring to mind - but the traffic getting into the Seattle area from these areas is HELL! Truly. Also, lots of wetlands and protected areas with tighter regulations.
King county is right out - too expensive!
Pierce county is out for me - too much sprawl. Eastern parts (Orting, Roy) are nice, but you have to drive through endless strip malls to get anywhere. Yuk.
Kitsap county can be nice, as well as Mason county - ferries can get you into Seattle without so much of the traffic and sprawl driving you get in other areas. Prices are okay - soils are VERY depleted and gravelly, due to glacial scraping. The cultural vibe is more conservative and the military influence is more pronounced here, too.
Thurston is a bit expensive, but rare good deals can be found, and location close to Olympia is a plus.
Grays Harbor county has AMAZING good deals, but it's really a drive from the I-5 corridor - same with Pacific county.
I ended up focusing on Lewis, Clark and Wahkiakum counties; some good train connections, close (enough) to I-5 corridor, and prices were rational. We are finally buying in Lewis county, and the regs seem pretty relaxed. Very rural vibe. We're getting 10 acres at 660 feet elevation with a year-round creek, mature fruit
trees, old garage and barn, fenced paddocks, 1/4 wetland, 1/4 cleared and 1/2 woodlot with mature softwoods PLUS a ratty enclosed double wide for $72K. We're only a few miles from the 2 premier
permaculture nurseries in W WA, and there are several
permie homesteaders in the general area. I'm delighted.
As many will tell you, you can get away with quite a bit if you don't want to teach or bill yourself as a learning center of any kind - just live privately and get along with everyone. The forums here will be invaluable for you when it comes to the specific quirks of your particular area, and finding like-minded friends.
Good luck!