Each church has it's own money and is free to do what it wants with it. The problem comes if taxpayers money gets involved, or if it is used as a way to avoid tax in any way whatsoever. If not then they are completely free to do what they want, spend on fancy gold chairs for no reason if they want to, the church is good at wasting money like that.
This is really a question between the leaders and the congregation. If the congregation is willing to pay for their leaders living expenses in exchange for their guidance and loyalty, then this is not something I would want to see the government interfere with. If abuses or criminal activity are occurring then appropriate actions should be taken.
I do not believe that Mormon church leaders should be paid living expenses. This should come under the Mormon belief of tithing, where believers pay one tenth of their income to the church. I do not feel that the living expenses of leaders should come out of this money, as they have to pay their own tenth as well.
No, Church leaders should not be paid living expenses because they are supposed to be religious leaders simply due to their belief system, not because they are trying to get rich. They should be totally selfless when leading the church, and everything materialistic should come secondary. That is the only way to lead.