A person who lives by using others' resources or support

A "leech" is a term used to describe someone who exploits others for personal gain, fitting the description of someone who lives by using others' resources or support. Patron is someone who supports or sponsors an individual or cause, rather than relying on others. Beneficiary is someone who receives benefits or advantages, but not necessarily in a parasitic manner. Contributor refers to someone who adds or gives to a cause, not someone who depends on others.