Is it permissible for a father to buy an apartment from his son through real estate financing from a bank, with the property mortgaged to the bank, and then for the son to lend the father the amount after receiving it from the bank?

There are two scenarios for this issue:

The first: That an agreement is made between you to complete the transaction with the bank, such that the son receives the money and gives it to his father, and the father returns the apartment and pays its price to the bank with an increase. This scenario is prohibited because it is a stratagem to conceal usury (riba). The reality of the matter is that the father took money from the bank to return it with an increase, and used the apartment as a means to obtain this loan. The sale here is fictitious and not intended.

The second: That the father genuinely intends to purchase the apartment through a real sale, such that the bank buys it at market price, then the father buys it from the bank, takes possession of it, and it is under his guarantee. This is a form of Murabaha financing, which is permissible. After this, there is no objection to the son lending the money he received from the bank [to his father], but it is not permissible to agree that the son benefits from the apartment during the loan period, because in that case, it would be a loan that yielded a benefit to the lender.