freeloader — to take advantage of others for free food, entertainment, etc.
leech — Margaret, 1893–1974, U.S. historian, novelist, and biographer.
parasite — an organism that lives on or in an organism of another species, known as the host, from the body of which it obtains nutriment.
sponge — any aquatic, chiefly marine animal of the phylum Porifera, having a porous structure and usually a horny, siliceous or calcareous internal skeleton or framework, occurring in large, sessile colonies.
