Preferably debt free. Mortgage repayments will not normally be allowed to be more than 35% of your net income.
Speaking from personal experience, I was enquiring about a mortgage and have a car loan of €500 per month. This effectively brings down my repayment capacity by that much (e.g. if a person had a bring home pay of, say, €3500, amount of other committments is deducted from this, and then used to calculate available repayment capacity) Quite a shock when you see the difference it makes to the mortgage amount they could offer you! Advice would be to pay off all debts and then save, then apply.