I'm going to take a lot of "What she said" and add:

In ancient Greece, priesthoods can be bought and sold and the only purpose of the clergy was to keep the temples and shrines nice and tidy and lead the crowds during festivals and sacrifices.  In return, the priest got his share of meat from the sacrificed animal.

But that was just in the public worship.  In private homes, the the head of the household functioned as clergy by leading his family in prayers and performing offerings to the household deities.