Afonso's place in Porto is a good starting point for any journey in Porto. It offers a central location, very close to a metro stop (with a direct connection to the airport). Everything is within walkable distance, so it is not really necessary to use the public transport to visit the city centre (maybe if you want to visit the port cellars). The apartment itself is ok, the beds are comfortable and it is always nice to have to ability to prepare your own meal. However there are some remarks. First, for a business Airbnb it would be nice if for example there are some essentials like olive oil, salt & pepper and enough toilet paper for the entire stay (we stayed in Lisbon in such an apartment, that provided these things).
Second, the bathroom is nice. Take your own shampoo with you. There is a bathtub, but the boiler doesn't have enough hot water to fill it. We tried taking a hot bath, it is not possible. Third, the apartment needs some maintance. There are some dangerous situations in the apartment. Two guests (including me) of our group got an electric shock from the air extractor in the kitchen, so do not touch the buttons. Also in one of the bedrooms there is a nightlamp, it was not working, we didn't mention it but at last we discoverd it has a broken plug. The remaining pin could still be in the socket. This should be fixed. There are some other minor things like a broken shelf in one of the kitchen cabinets. Overall it is ok.