Mortgage down payments don't have a single percentage that works for everyone; they vary depending on the initiative or program, the property price, the loan-to-value ratio, your income, and your client type.
Key points
Instead of just asking "What percentage?", ask the bank for a quote that outlines the acceptable unit price, the loan amount, the required down payment, expenses, and monthly installments.
Compare the down payment with the cash you'll have left after the purchase, not just the lowest figure.
The figures, fees and limits in this answer vary by bank and change over time — confirm them with your bank or the official source before acting.