He was a native Californian, something that's pretty rare even today and much more so when he was born.
He and his wife Norma bought what was basically a shack in the Oakland hills and worked on it all their lives. It's now a two-story house, but it's still not finished -- and Vance was fixing it up into his nineties.
He insisted that the only reason he wrote was for money.
He once went on a camping trip with his cats. They escaped instantly, and he spent the rest of the time looking for them. Fortunately, he found all five.
He wrote an Ellery Queen novel with the evocative title Strange She Hasn't Written. The publisher changed the title to something else, something so dull I can't remember it.
I also told some people the only anecdote I know about Vance. He rarely went to science fiction parties in the Bay Area, but he turned up at a Locus party once. A while into the party I looked around for Doug and found him having what looked like an argument with Vance. Turned out that Vance was insisting that Dixieland jazz was the only form of jazz worth listening to, and Doug said he thought there were some later styles that were pretty good. Later, when the Vances went to leave, Jack turned to Doug and said, "So, do you want to jam some time?"
Everyone I told this to, all of them people who knew Vance fairly well, said that that was the kind of person he was. He liked to argue, but if you knew anything about music he could talk to you for hours. (And no, Doug never took him up on the offer. I sometimes wonder what would have happened if he had.)