Zapping, using an electronic card is probably the best inter-modal transport payment system for Lisbon. Before you buy a ticket, consider how you’d like to use it. For the train alone? Or for a combination of train, metro, bus, tram and ferry? You’ll need to buy the right ticket combination for all the types of transport you’re planning to use. Once you’ve bought the card (50c) and loaded it with credit, you can use it to pay-as-you-go.
The Lisbon card is also useful but how early you start using it will depend on what you want to do with it e.g. visiting Belem or Sintra, museums and galleries, travelling around Lisbon? It might be worth getting the 72 hours Lisboa Card from the Information Centre in Lisbon city when you’ve found your feet.
In Carcavelos, you’ll be just 20 mins by train to Lisbon’s city centre and 10 minutes to Cascais.
Access the timetable here.
Do you plan to hire a car to travel around in? In addition to airport based car rental services there’s a non-airport based service in Cascais. And if you can find a space, there is metered car parking in front of the apartment.