Beware:
The apartment has a lot of mold in both bedrooms. Stains on the pillows. Host expects that two people always sleep together in a bed even if you say you're three friends, an extra bed costs 10€ and they refer to the house rules where this is stated in a somewhat mixed Portuguese English language. The host gave us new sheets for a third bed anyways without us paying for it but they felt like this was normal. No air-conditioning. Right under the apartment there is an Erasmus bar where some 50 people drink on the street, scream, do cocaine and go crazy, not only on the weekends. The bathroom is nice but the kitchen is not well equipped. Basically you can not cook in this apartment.
The good thing is, the apartment is very central and you can get anywhere by foot. Also the hosts had a lot of good tips where to go, what food to taste and told us about Porto which was really great.