@tamarakko I know someone who was working for her teacher's wife small business (and she took it for her undergraduate thesis. Of course they paid her a low wage despite she had 'college student' knowledge and ability, the only different is 'title' without the title, she's only a high school level)
And sadly there's higher chance that's what happening to Kiyo. If she didn't want to take the job, Mother could look for another aunty although it took times, beside there's no special taste in Kiyo's dish (that probably could change as time passed) so if she wanted a higher payment, Mother might choose other than her (that won't sleep, eat, bath, and using electricity in the manor) cause before her appearance, there's no problem with cleaning issue. Not to mention, she's treated as meiko (allowance and day off) while in fact she's not, she might working in there for years or working as Sumire's personal helper when Sumire can be a geiko and have more money to support both of them