Green’s Dictionary of Slang

the voluntary donation of her earnings that a new prostitute gives her pimp on joining his stable n.

1972		Milner & Milner Black Players 41: If a pimp finds he is hitting on a bitch successfully he announces to her that he is ready to be chosen, and asks that she present him with her choosing money, that is, money that she will give him for the honor of joining his stable.
1981		A.K. Shulman On the Stroll 55: He’d never heard of ‘choosing money,’ much less a thousand dollars of it. He didn’t even know that a ho chooses her man, not a man his ho.