"Cum and done" refers to a woman who is willing to have
sex for
money (a hooker), but as soon as the
guy cums, she is immediately out of the mood, takes the cash, puts her clothes on and leaves.
As opposed to a more expensive escort, who is paid by the hour, and even if the guy finishes after five minutes, will stay with him to cuddle, kiss, wait for a second erection or even just to talk.