It does depend a little bit on whether you’re a resident in Portugal and how stable your income is considered to be. A freelancer, for example, might have more trouble than someone in a normal job.
Most people seem to be offered somewhere around 70% LTV so you would need a 30% deposit. You also need to factor in the costs of purchasing which are roughly around 10%, although they can be a bit less. So you might need to be thinking about having 40% cash to hand plus an emergency fund before buying in Portugal.
This is based on mortgages from Portuguese banks. You may be able to get a mortgage in your home country, but it probably will have a higher deposit than 5 or 10% if it’s being used to purchase a property abroad.