We stayed in Ricardo's appartement for one week to enjoy Porto and the Duoro valley. It is centrally located in a non-touristy neighbourhood. The city center is a short walk up north for 15 minutes, and as a bonus you pass the Eiffel bridge. A short walk down south (10 mins) a big shopping mall is located.
Richardo is a helpful host, he was attentive during our stay. There was a small issue with the outside door which was quickly fixed.
The appartement is new and clean. It is a bit small but for during our stay (7 days) this was no problem for me and my partner. However if you have a lot of large suitcases it might not fit.