Is it permissible to give zakat to someone who is in debt, knowing that he has a job and will live in an apartment he bought with an interest-bearing loan after one year?

Borrowing with interest without necessity is one of the major sins. It is not permissible to borrow with interest to buy an apartment if the borrower is able to rent a house. This man should be advised to repent from dealing with usury. As for giving him from zakat, it is permissible if he is unable to repay and is unable to combine debt repayment with his and his family's expenses.