I can answer two small questions on this one:
I recently moved with my company. Taxation of the moving stipend depends on the characterization of it. Almost all of my moving expenses were taxed, including the "lump sum" portion to cover any misc. fees. My company very nicely grossed this up (paying the 40% marginal tax rate on it (the pay stub showed $14,000 with a $10,000 lump sum), however because of this, I ended up not being eligible for my Roth IRA (if I had known this before investing for the year I could have done it differently, but I didn't). So, long story short, assume it will be taxed, and figure $6,000 (unless your maginal bracket with all other federal and state deductions included is lower).
For Airbnb cost, this really depends on what you're looking for. You can check out the monthly rate for places now for the comfort of lower CA. You'll have to decide for yourself weather the $1000 for bare bones/$1300 for slightly more is worth the "entire place" or $500-$700 for a solo room (from the PDX Airbnb site, December to January) are acceptable to figure out where you should live with very little commitment (I would say it obviously depends, but currently with my stubbly lady 'stache I would accept this for no more than a month).
Happy decision making!