I had a great month-long stay at Carlos' place. I do not speak any portuguese but I felt welcome and at-home. Carlos kept the kitchen and bathroom super clean at all times and even changed my sheets and cleaned my room once a week. Another reviewer complained about their room being entered but Carlos is just keeping it clean.
The apartment building felt super safe and secure as there is a security guard at the front.
Some things that I wish I'd known before booking: the apartment does not have AC. A fan is provided but it is not very strong. I visited during summer (Februrary) so it was quite hot in my room on some days. Closing the blackout shades helped with this. Additionally, possibly because of the plants, there are mosquitos. I bought an outlet repellant and this helped. Finally, the noise from the street can be loud and the window is hard to close and open. After a few days, I got used to the noise and it didn't bother me.
Not fancy but affordable. Great location and host.