Overall, Carlos’s place was good and served its purpose as a place to sleep at night. However, for those traveling during the winter, be warned that the apartment gets very cold at night, there is a small portable heater that doesn't really provide much heat, so make sure to bring warm pajamas for the night. The daily ration of hot water was good, sufficient for two people to shower back to back. But, since the apartment gets cold at night, if you want to enjoy a few extra minutes of a warm shower, be mindful that this might leave your companion without enough hot water. One thing to note is that the walls are extremely thin, so you can hear everything, I’m a heavy sleeper so this was not an issue for me. But keep this in mind if you're a light sleeper or sensitive to noise.
I would stay at Carlos' place again, and I recommend it as it is centrally located and close to major attractions. The metro is only a 4-minute walk away.