Is it permissible for a real estate company to sell a residential building in installments, then transfer its ownership to another party in exchange for a cash sum, with the latter collecting the installments and transferring ownership to the buyers later, and with the building's price being reduced for him to profit? And is this transaction considered selling a debt to someone other than the debtor, or selling a debt for a commodity (the building), or a permissible sale and purchase?

If an apartment is sold in installments, its ownership cannot be transferred to anyone other than the buyer, because it has exited the seller's possession.

As for the installment price (the debt), selling it to someone other than the buyer has two scenarios:

1. Selling it for less immediate cash: This is forbidden because it involves riba al-fadl (usury of surplus) and riba al-nasi'ah (usury of delay). 2. Selling it for an immediate commodity (other than gold and silver): This is permissible under two conditions: The buyer of the debt must be able to collect it. The seller of the debt must not profit, meaning he should not take a commodity whose value exceeds the value of the debt.

Based on this, it is absolutely impermissible to transfer the ownership of the apartment from the buyer to anyone else. It is permissible to sell the due installments for an immediate commodity under the mentioned conditions, whereas selling them for less immediate cash is forbidden.