Arremango comes from the verb arremangar, which literally means "to roll up your sleeves", as if preparing for hard work. It's a powerful and uncommon word you won't find in a typical Spanish textbook.
In "Billete", Peso Pluma uses it as slang in the phrase "Arremango pacas" to mean he effortlessly grabs or scoops up stacks of cash. This single word vividly paints a picture of his success and the flashy lifestyle he's describing in the song.
Peso Pluma and Tito Double P are not subtle in this song. "Billete" is all about one thing: being in love with money. The whole track is a description of a very specific lifestyle, one where they travel constantly by boat and plane, but as they say, "no ando de vacaciones" [I'm not on vacation]. This is all business. The business involves private parties with "pura fresa niña mala" [pure preppy bad girls] and rolling around in a white Cherokee, maybe looking more low-key than he actually is.
He shouts out Atlanta as his second home and makes it clear the streets are "calientes" [hot], but he's motivated by friends who aren't around anymore. He says "Sigo firme en mi camino, por ellos no voy a pararle" [I'm staying firm on my path, for them I'm not going to stop]. The goal is clear when he talks about counting "presidentes" [presidents], which is slang for US dollars. The song's hook is blunt and gets right to the point: "me enamoré del billete" [I fell in love with the bill/money].