What is the ruling on buying an apartment offered by an institution at cost price, by installments with a small usurious interest? And what is the ruling on a husband taking out a loan from a bank with usurious interest if this is the only means available to him to buy his share of the apartment?

It is not permissible for a Muslim to borrow with interest, whether from their workplace or elsewhere, because this is precisely usury (riba), which is forbidden by Islamic law. Allah (the Most High) says: "O you who have believed, fear Allah and give up what remains [due to you] of interest, if you should be believers. And if you do not, then be informed of a war [against you] from Allah and His Messenger." It is not permissible to share an apartment if the other partner's share is borrowed with usury, because that falls under cooperating in sin. Purchasing housing with usury is not permissible because it is a need, not a necessity, unless there is not enough left from one's salary to rent accommodation and one can find no other way to obtain it except through usury. In such a case, it is permissible due to necessity.