What is the ruling on taking a sum of money in exchange for replacing an employee housing unit with aملك housing unit, such that the first beneficiary completes the installments for the ملك housing unit and both houses remain for the second party?

We do not know the nature of the company housing. If it is granted to the employee on loan, then it is not permissible to dispose of it except with the company's permission. Your doing so without their permission is considered an encroachment on people's wealth and consuming it unjustly. Allah Almighty says: "O you who have believed, do not consume one another's property unjustly but only [in lawful] business by mutual consent. And do not kill yourselves. Indeed, Allah is ever Merciful to you." However, if the company permits the relinquishment of your right to company housing in the manner mentioned, we see no objection.