You're not the first person to have trouble distinguishing who does and doesn't have moolah; I had a friend of mine try the game out after I released it on Itch and she had similar troubles. Basically, the people with hats or accessories of some kind (monocle, money-eyes, rosy cheeks) were the rich customers, while those without them were not (except for day 3, where it's entirely randomized and you have to use the MoniMeter). My initial concept was actually to have the kimono/yukatas have unique designs for the rich customers and just be plain for the poor customers, but I couldn't come up with any unique or interesting designs (I flipped through at least four different designs on Jo'on's alone), so I settled for just adding things on top of the five base suitors.
I'm glad you enjoyed the beeping. It's supposed to be the first few notes of the Theme of Eastern Story motif, but I think I cut the end loop off too quickly so the first and last note blend together. I blame GameMaker (and totally not the dev who has no idea what she's doing). I wanted there to be more sound effects (the biggest one being the opening/closing of the shutter) but I couldn't make them very well with my voice (plus I didn't want to deal with the GM2 audio system). Anyway, thanks for enjoying the game!