Is it permissible to sell an apartment to one's mother through a real estate financing system in order to obtain money and repay what the mother paid to help her son with his marriage, or is this considered a form of circumvention?

It is forbidden to deceive the bank in order to sell a property under the Murabahah (definition) system, where the bank buys the property from you and then sells it to your mother, and gives you the price while the apartment remains in your possession. This is because it involves falling into usury (riba), as the transaction ultimately leads to a usurious loan, which is unanimously forbidden. Furthermore, it involves deceiving the bank, and deception and cheating are forbidden.

As for real estate financing provided by usurious banks, which involves paying the price on behalf of the buyer without the bank actually buying and then selling, this is usury (riba) and it is not permissible to engage in it.

However, if your mother helped with half the price of the apartment and you have one brother, then justice dictates that you give your brother a similar amount, taking into account the depreciation of the currency, or that she takes back what she gave you.

Money can be collected by forming a cooperative (jam'iyyah) or through Tawarruq, which involves buying a car in installments and selling it in the market for cash. Tawarruq is permissible according to the majority of jurists.