Every religion collect money from its believers.
Judaism collect 10% of annual income from each Jew excluding poor in the name of tithing.
The same, in Christianity, every church collect money from members of church in the name of church-tax. They collect it on basis of monthly, quarterly or annually.
In Islam, 2.5 % of annual income collected form each believers in the name of zakaat.
What are they doing with this money?
They are spending to built their religious places, maintaining it, giving salary to religion’s employees such as bishop, paster, imam etc., they spend most of money for evangelism, conversion etc., also some of money goes missing in corruption of clergy as where there is lot of money, there is a corruption.