Most lenders in Portugal will require a down payment when you apply for a mortgage. The down payment is a percentage of the purchase price of the property that you pay upfront, and it is typically required to reduce the lender's risk and ensure that you have a financial stake in the property.

In general, most lenders will allow you to borrow up to 90% of the value of the property, which means you will need to have a down payment of at least 10%. However, some lenders may require a larger down payment, especially if you have a low credit score or a high debt-to-income ratio.

The size of the down payment can also affect the terms of the mortgage, such as the interest rate and fees. A larger down payment may result in a lower interest rate and lower fees, while a smaller down payment may result in a higher interest rate and higher fees.

It is a good idea to carefully consider your financial situation and budget when deciding on the size of your down payment. You may also want to seek the advice of a financial advisor or mortgage broker who can help you understand your options and make an informed decision.