This is something I think about a lot: a while back, in a game in which we were playing a gang of criminals turned neighborhood protectors, the DM asked us to be prepared to talk about where our characters slept. When they weren't being adventurers and running a shady business, what did their lives look like?
I found myself taking a lot of notes on what the other players brought to the table. I already knew their characters from weeks of play, but it was amazing to get a glimpse into who they were when they weren't risking life and limb in pursuit of gold and power.
The characters:
Bronte
Goliath eldritch knight fighter
Bronte occupies the top floor of a ramshackle tower that has been built out of the remnants of a crashed airship. His bedroom has been pieced together from the ship's cockpit. His rooms in the tower are absolutely crammed full of junk and scavenged debris. Scrolls and books about magic litter the floor. He also has the bad habit of leaving half-eaten containers of take-away food strewn throughout his flat. Bronte smokes innumerable cigarettes on his balcony while he watches the to-and-fro of the city's residents.
Hayseed
Human circle of dreams druid
Hayseed is an unkempt country bumpkin who seems ill-adjusted to life in the big city. Hayseed has a shaggy beard, dirty threadbare clothes, and a smell that one would associate with a countryside barn. Hayseed rents a small house nestled among the gigantic trees of Kenweth Park. Inside, Hayseed's house is immaculate and the many potted flowers he keeps lend the place a highly perfumed and fresh scent. He has a piece of furniture that looks like a library card catalog, but inside it has neatly organized packets of seeds.
Kallisto
Half-elf college of whispers bard/hexblade warlock
Kallisto has carved out a bedroom in the basement in the basement of the gang's munitions factory. No one knows about this room; it's tucked away in storage space where no one ever goes. Although Kallisto takes pains to present herself as a well-dressed, stylish business woman, her room is extremely spartan. She owns very little in the way of personal effects, save for one solograph print of her with her bother, an anarchist who is currently on the run from the vengeful forces of the law.
Gumdrop
Gnome chaos sorcerer
Gumdrop maintains an apartment above a candy store. The street is quiet and the families who live on it are solidly middle class. She never keeps food in her apartment, preferring to eat at the noodle stand down the street. Her apartment is absolutely filled with plush animals. Anyone who comes into her living space is likely to be terrified by the quality of plush animals lurking throughout the apartment--it isn't cute, it's vaguely but intensely off-putting.
Wax
Changeling assassin rogue/battlemaster fighter
The party knows Wax as a stone-cold, hardened killer; due to assuming and discarding identities continually as a changeling, he has little sense of self--no inner core. The other characters in the party are honestly a little afraid of him. What they don't know is that he has a secret life of warm, prosaic attachment. Wax rents a room in a working-class family's home. When he returns to his quarters, he assumes the likeness and persona of an utterly plain factory worker. When at home, he partakes of his landlords' family life--he takes his meals with them, sharing in their joys and sorrows. These moments are the only time when he actually enjoys life.