@Alire_25 

Since your client is trading labor for rent, the rent is an expense and the labor provided is income.  Create a bank account called 'Barter Exchange' or 'Barter Control'.  Enter the bill for rent and pay it using the Barter bank account.  Then, create an invoice to issue to the landlord for the labor provided.  Receive payment on the invoice using the Barter bank account.  That will book income and expense for the barter and the Barter bank account should be $0 after the transactions.  The only expenses that reduce net income for your client are the actual expenses your client incurs in performing the labor like supplies, etc.