I may have the option of moving to SF for work in the next 6 months and am trying to get a feel for what options are available.
Since the general consensus is that housing is ludicrously expensive I was tentatively thinking about RV or boat as a more frugal option.
You can't get away with that using a full size class A, or even a little pop-up trailer.
Real RVers know the real problem of RVs for road trips or urban live aboard is finding a dump station downtown. I suppose you can always use the local mega corp parking lot. Antics like that are what leads to attempts to ban RVs, of course.
Boat living definitely happens.
If you decide you prefer land, and your work is near BART, the East Bay (esp. Berkeley, Rockridge) offer much better value.
If you like the idea of taking a ferry to work every day, and work downtown, consider Marin County north of the GG Bridge.
I'm surprised no other comment mentioned Jacob of Early Retirement Extreme[1]. He blogged about living in an RV at the Pacifica RV park to save money. Unlike Mr. Money Mustache who is often derided in these comments, Jacob was extreme, and recognized it. Instead of living in an RV to bootstrap a startup, he had a normal tech job and saved tons of money to invest and retire on the dividends (I'm simplifying).
You've probably seen a modern version without even noticing. Usually the give away is the side mounts for water. A modern new conversion van is like $75K so in a big enough city its cheaper than any real estate, not so much in the country.
They're pretty comfy if you're short. If you're living in a city, supposedly all those people live there because "theres so much to do 24x365", so other than sleep and sex you should be outside the vehicle at all times. Reminds me of my honeymoon cruise ship cabin, that was a dumpy broom closet but we were too busy to notice.
The mileage tends to be excellent. How many MPG would my wife's Prius get moving an entire house? 60 MPG divided by probably hundreds of trips = not so good. Rialtos get like 15 MPG, or so I hear, which isn't bad. I imagine it depends on the exact model and condition of mechanicals.
I always thought SF was on the ocean, and the obvious live aboard vehicle is a sailboat. Of course marina space is probably expensive and unavailable. Perhaps if you moored offshore in wifi range of work...