bleed someone dry (or white) drain someone of all their money or resources.
☞ Since the late 17th century bleeding has been a metaphor for extorting money from someone. White refers to the physiological effect of losing blood.
1982William HaggardThe Mischief-Makers Her husband had been a wealthy man, the lady's solicitors sharp and ruthless, and her husband had been bled white to get rid of her.