mormon missionaries will tell people that you only have to pay 10%

which, by itself, is a shock for most people, but what they DONT tell you is that once you get to the temple you have to agree to the law of consecration which requires you to give 100%, that you have to:

"covenant and promise before God, angels , and these witnesses at this alter, that you do accept the Law of Consecration as contained in the Doctrine and Covenant, in that you do consecrate yourselves, your time, talents, and ***everything with which the Lord has blessed you, or with which he may bless you***, to the Church of Jesus Christ of Latter-day Saints, for the building up of the Kingdom of God on the earth and for the establishment of Zion."

"mormons only pay 10% (tithing) of their income" is a whopping lie =) the figure is missing a zero--100% (if the church requires it of you)