Green’s Dictionary of Slang

down adv.⁴

(US black) owing, deficient in.

1922		Joyce Ulysses 169: – O, it’s a fine order, Nosey Flynn said. They stick to you when you’re down.
1930		L. Bogan ‘They Ain’t Walking No More’ 🎵 Sometimes I’m up, sometimes I’m down, / I can’t make my living around this town.
1952		Hal Ellson Golden Spike 199: ‘Have you got anything?’ ‘I’m down and busted,’ Chico answered.
1961		H. Ellison ‘At the Mountain of Blindness’ in Gentleman Junkie 63: I’m only down a few bills. Stake me, Porky.
1975		E. Torres Carlito’s Way 24: Who else is going to [...] see you go for a yard when your bread is down.
1981		D.E. Miller Bk of Jargon 292: I’m down five bucks.
2005		B. Coleman Rakim Told Me 42: [S]hortly thereafter, the Amazing V left the group [...] Down one MC, Mixx knew just the person to fill the spot .

In phrases

down in

lacking in, short of.

1889–90

Barrère & Leland Dict. of Sl., Jargon and Cant.