What is the ruling of Islam on the sale of "the key," prevalent in Morocco, where a shop is sold for 20,000 dirhams and the seller subsequently obtains an ijaza (usufruct right) for 150 dirhams?

It is permissible to sell the 'key money' or 'khulu al-rajul' if the seller is a continuous tenant of a shop, whereby he relinquishes it to another person in exchange for a sum of money and a monthly rent agreed upon by both parties. The reason for permissibility is that the seller has acquired ownership of the usufruct of the premises, so he may relinquish his right to another person and lease the usufruct he owns, provided that the buyer uses the premises for the same purpose as the seller, or for a purpose that causes less harm.