I love laundromats and have long daydreamed of owning one.
The very best one I ever used was a great case study, I think.
Always well-used.
Had a machine to convert bills to coins.
Sold soap to those of us who forgot theirs again.
Great prices.
Beautiful esthetic: lovely paint job, local art work.
Coffee shop! Coffee, comfy sitting area, wifi, TV, toys for kids.
Huge machines (very efficient for user).
Plenty of large tables for folding.
Bright, clean.
Friendly patrons.
Washrooms.
The catches:
Unstaffed on weekends. This was a nightmare, as many things needed attending in any given hour (coin machine, etc).
Coin machine broken into multiple times over short period.
No way to reach any staff/owner when things were going poorly.
Frequently ran out of coins in the machine, or of soap.
No unscented soaps for sale.
I think those catches are easily remedied: staff person, unscented soap.