>>50129300
She claims to run a yakitori stand in vague conversation with the people she escorts through the forest to deflect away attention from herself, but there's zero evidence she actually does so, and she's never shown ever actually doing so on-panel (not even during Hakurei Shrine festivals where Mystia shows up), or while she's mulling over her life in her CiLR chapter where she's shown to barely even eat because she enjoys being miserable.

The obvious truth is that Mokou adds less to society than the average fairy, and her sole source of income is probably pocket money given to her by Kaguya.