Is it permissible to use the amount of rent that the contractor will pay as an installment for a new apartment instead of it being rent, in the event of his delay in delivering the agreed-upon apartment?

The aforementioned condition is impermissible because it is a loan with interest. The permissible contracting agreement is that, in case of delay in completing the work – without a compelling excuse – compensation be stipulated for the actual damage incurred. Therefore, it is not permissible to take the rental amount, and the matter should be referred to the court or to arbitrators to rule on a real compensation for the damage. It is not unlikely that the contract itself is initially invalid due to the invalidity of the condition. In this case, you take what you paid as an advance, and the matter concludes.