First Estate was the clergy, consisting of members of religious orders. Number of problems: absenteeism (many bishops never visiting their diocese, which is an area made up of a large number of parishes), plurality (bishops would hold more than one diocese, which contributed towards the problem of absenteeism), exemption from any taxes, and the monopoly of Catholicism over French people (wide reaching powers of censorship, provision of poor relief, conductor of marriages and burials, and acting as a sort of Ministry of Information for the government)
The Church was the largest single landowner in France (owning about 10% of the land) and received most of its wealth from collecting the tithe, a charge paid by landowners to the Church based on the proportion of crops they produced (this varies across France) which provided the Church with around 50 million livres per year.
This money was supposed to provide for the parish priests, sustain the poor relief systems and upkeep Church buildings - but much of it went into the pockets of bishop and abbots. Highly resented by the peasantry and ordinary clergy.