Can an elderly woman allow her poor brother to benefit from her money to buy a store in his name, provided that the store's profits return to her to repay the original amount in installments?

It is not permissible to take or invest this money except with the owner's permission, as the Messenger of Allah, peace and blessings be upon him, said: "The wealth of a Muslim person is not lawful unless given with their willing consent." If the woman permits her brother to take the money in a lawful manner, such as a guaranteed loan or a permissible investment like Mudarabah (profit-sharing) or a partnership, then there is no objection, and the brother's hand would then be that of a trustee.