António is really helpful and nice to talk person. He lives next door to flat that he rents, so there is no problem with key delivery. The flat is very clean, with new equipment (it has everything you need) and has a artistic look. It's located in the city center, close to metro station (5min), close to Douro river (15m).
If I would come back one day to Porto I would definietly rent the same flat again! :)