bloodsucker
1. Someone who preys (monetarily) upon a person or people through deceitful means, as through extortion or by means of a con. That insurance salesmen ended up being a total bloodsucker. He signed me up for coverage that I can't use, and it has cost me a fortune!
2. One who depends upon the generosity or resources of another person in a parasitic manner. Your friend seems like a bit of a bloodsucker. He kept asking everyone to pay for his drinks all night long.