SHAFAQNA – The Grand Ayatollah Makarem Shirazi answered a question about commercializing some parts of the Mosque.
Question: Can parts of the Mosque like the basement be converted into kitchen, or when modernizing, some shops are built for renting?
The Grand Ayatollah Makarem: Under any circumstances, renting Mosques is not allowed; must explain that, sometimes parts of the Mosque are converted for income; for example the basement is converted into kitchen to rent it, or when modernizing the Mosque, some shops are built for income and to spend the income for the Mosque; all of these are not allowed according to the religion; the Mosque cannot be rented or a shop to be separated, also the basement cannot be rented as kitchen, because going down to whatever level still is part of the Mosque and rules about the Mosques apply. Of course if these changes have been done without permission, we do not say to demolish it, but they must be used for the Mosque and not for income. For example if it is a shop, block the outside door of it, and open a door from inside to be used a room for the Mosque. Also it must be noted that there is no problem if from the beginning there was an intention to build shop and things like that.
Source: PERSIAN SHAFAQNA