The communication with Carlos was very good. His mother welcomed me when I arrived and I only saw Carlos during checkout. The place was quite spacious and would easily fit 4 people. Comfy bed and comfy sofa(bed). The kitchen was very small but had the basics needed (cutlery, glasses, gas cooker/oven and a big fridge). The bathroom was ok and basic. The internet (very important!) was very good.
The flat was nicely located 10 minutes from the Metro station (it's inbetween 2 stations) and the beach was 2 blocks away. There was like a "concierge" in the lobby until about 8pm. Copacabana is a very safe area and walking around at night is not a problem.