We stayed for one month at Luis’s condo and found him and his wife to be wonderful caretakers and respectful hosts and we very much enjoyed staying in the apartment. They met us when they said they would, they showed concern with any reported issues (all very minor), cleaners came weekly at the stated time, nothing ever went missing, they gave great local tips, everything in the apartment functioned well... I could go on and on. The kitchen has a washer/dryer and is stocked with any dish or appliance we could think to want to use during our one-month stay. The furnishings are modern and very comfortable (including the pull out couch, which we tested one night for kicks). The WiFi and air conditioning work very well and the TV has more channels than we had time to watch!
The building is not in a noisy area, I always felt safe walking around at night, and it is a convenient three-block walk to the main shopping street and has several cafes and inexpensive restaurants on the same block. As for Luís, he speaks excellent English and he or his wife responded within minutes to any email or text message. They are extremely professional.
The only real downside we experienced is that this is a building with mostly air bnb rentals and there can be some guests who gather in the hallways and get a little loud as these people are on vacation and not working and we were there for work as well as sightseeing. Also not everyone is great about shutting the front door so we made sure to lock and deadbolt our door when were inside. The late-night noise was only an issue two nights in 30, which is a pretty good ratio! So we wrote it off as a minor inconvenience. Also this has nothing to do with Luis as a host or his apartment.
We would definitely stay again should we find ourselves in Porto. Rent from them - you will not regret it.