Is it permissible for me to own my father's apartment, which he bought with his money from an interest-based bank, and benefit from it after repaying what he paid for it and completing its price?

It is permissible to purchase an apartment from one's father if the purchase contract fulfills the conditions, even if its price originates from ill-gotten wealth. This is because the unlawfulness of the money is tied to the father's liability and not to the object itself. As Ibn Abi Zayd mentioned, citing Malik and the people of Medina, Ibn Rushd explained this by stating that the forbidden nature is associated with the seller's liability. The price must be determined at the time of concluding the contract, and it is not valid to purchase it for the price he bought it for plus the cost of its renovation if that amount is unknown and unspecified.