Does the apartment bought by the father for his married son become the son's property immediately, or is it considered an inheritance to be divided among all heirs after the father's death?

Parents must be equitable among their children in giving, and it is not permissible to favor one child with a gift over their siblings, based on the Prophet's (peace and blessings be upon him) saying: "Fear Allah and be just among your children." This is also because such favoritism causes envy and hatred among them. However, it is not obligatory to equalize them in spending (nafaqah), which is determined by the needs of each individual. If a son needs housing, he may benefit from housing provided by the father, on the condition that this is for usufruct and not ownership. Upon the father's death, the apartment is divided among all heirs according to Allah's decree. Justice in spending means giving each person what they need, even if it is not identical to what is given to others.