Is it permissible to pay a sum of money to purchase remaining months for retirement, with a down payment and the rest in installments?

This type of sale is impermissible due to several prohibitions:

1. Gharar (Uncertainty): Because it is the sale of an unknown thing that may perish before its benefit can be realized. 2. Selling what one does not own: Because the seller does not own the future months; they may die before then. 3. Ghabn (Deception/Unfair Advantage): As the buyer purchases the months for less than what can be realized during the work period. 4. Riba an-Nasi'ah (Usury of Delay) and Riba al-Fadl (Usury of Excess): Because it is the sale of cash for more cash, deferred, and the small upfront payment is the price for the much larger expected return, which constitutes usury (riba).