Is it permissible for a poor, married young man with children, who is disabled, to take an amount of 15,0 Egyptian pounds from his mother, on the condition that she takes its profit throughout her life, and that the money devolves to him after her death, knowing that one of his acquaintances invests the money, and that he has two brothers, one of whom is wealthy and the other well-off, and that his mother owns a house worth 400,0 Egyptian pounds?

Your mother's wealth does not permit you to take her money without her permission. You must adhere to her condition regarding what she has given you. If her gift is contingent upon her death, it is considered a will (وصية), and for it to be valid, it must not be for an heir unless the other heirs approve. This is based on the Prophet's saying: "There is no will for an heir unless the heirs wish it." Therefore, it is not permissible to seize the amount without her permission and consent.