Money is the only thing on the speaker's mind here, and the poem shows how it takes over. The first stanza is almost a loop: days of thinking about how to get money, then how to borrow it. The repetition feels like a worry that won't let go.
The second stanza turns strange. "Son of my money" sounds like a joke or a chant, and "a rose is a rogue / for money" twists the old idea of the rose as a symbol of beauty. Here even something lovely seems to have turned shady, as if everything is judged by what it costs or earns. The title's "rap" fits the clipped, rhythmic, almost nagging sound.
In the last stanza, words "dissolve into mist." Language and perhaps poetry itself seem to fade, while the practical need to pay for food remains. The mood is anxious, tired and wryly bitter, with a dark humor about being squeezed by basic needs.