Interesting thought! Perhaps a photographer with either hoaxes or pornography in mind would have a strong incentive to develop their own. Yet if they were young transients, it seems likely that they themselves would have been living in a rented room, so maybe not.Although I do wonder what they do if they happen across a pic of a crime or something like that.
I've often though about the pics an old school film processor saw in their career. You can imagine
It isn't that complicated to buy a red light bulb and fit the bathroom window with a blackout screen. My mother did it as a hobby in the 1950s, and dad even made her an enlarger to use.