Is buying an "off-plan" apartment with a down payment of monthly installments until its completion, and paying the remaining amount after receipt, permissible (halal) or forbidden (haram)? And are the file fees ($150) permissible or forbidden? And is the buyer's relinquishment of their payments (e.g., $12,0) with a request for additional profit ($2,0) permissible or forbidden?

It is permissible to purchase an apartment off-plan if its specifications are clearly defined. This contract is called "Istisna'a" (manufacturing contract), and it allows for the payment of the price in advance, deferred, or in installments, with a specified delivery date. It is also permissible to pay file expenses, which are fees for reviewing the case.

The buyer is not permitted to sell the apartment before it is built and received, because this is considered selling something non-existent, except back to the original seller. If the apartment is mortgaged as a guarantee for the payment of the price, it is not permissible to sell it except with the permission of the seller (the mortgagee).