Here's something that more experienced travels already know but which I feel the need to reiterate to make me feel just a little bit better about my own ignorance: when Europeans reference the 1st floor, they are speaking about what us Americans would consider the 2nd floor.
Our BnB host, Fabio, informed my wife and I upon our arrival in Porto that the keys to the apartment would be available in a lockbox on the 1st floor, and of course we marched right into the vestibule at ground level and tried to enter the code he provided. Surprise, surprise it didn't work. We reached out to Fabio, and he graciously drove to meet us at the apartment, explaining to us the 1st floor/ground floor mix up very graciously without making us feel like idiots!
Our experience was only up from there. The apartment was very well maintained and quite clean. Fabio told us that he hired a professional cleaning crew between guests, and it was very obvious that he was true to his word. Bedding was immaculate as were the shower and toilet. The apartment is also well situated in Porto a few blocks away from a major grocery store (Pingo Dolce) and several smaller markets and convenience stores that will serve you well should you find yourself in need of water, food, and any other goods.