Keep in mind Vancouver will cost you far more for a multitude of fees that will more than offset any savngs you get from property taxes compared to Oregon. Pretty much EVERYTHING except property taxes costs more in WA.
Food, gas, utilities, car registration is obscene, sales tax...
The most important suggestion was the one about being able to comfortably afford your payment without a roomie/renter/relative contributing. Bringing your brother in doubles the odds of someone being laid off, injured, or imprisoned, leaving one income to carry the weight. Also, I've found that even the best friends get sick of each other after several months of co-habitation. And when you are buying a home but your roomie is paying half the payments he really can't help but feel like he's a part owner and above obeying your wishes about upkeep, rules...
Do you really want to end up hating your brother? Better to rent a room to a stranger you'll be comfortable throwing out if you have to.