Lisbon is currently en-vogue and rapidly becoming a major startup-city as well as an important destination due to its cultural heritage, traditions and safety being one of the top-3 safest countries in the world.
Due to that, finding a place to stay for longer periods, specially in urban regions, is becoming increasingly difficult. Additional the regulation of digital platforms like AirBnB have further increased the costs for cities like Lisbon and Porto.
A good alternative to find a place is Uniplaces. Uniplaces is a digital marketplace focused on longer reservations for students, providing better deals for longer stays.
Other alternatives are traditional marketplaces for real-estate.
The best platforms in Portugal are:
To find attractive listings you should also look outside the city center. While these listings are more affordable, they also may offer other attractions like be nearer to the beaches or nature.
Due to the complicated public transportation setup, one should focus on areas near the major train lines, therefore it is advisable to look in Cascais, Sintra or Almada.
Having this in mind, you can take advantage of the favorable housing markets in those areas, while being able to fully enjoy being in Portugal.