Carlos could not have been more helpful. We stayed there with my (future) mother and sister in law and it was important for me they were comfortable and their experience was easy in terms of language and travel. Carlos assisted with helping my sister in law who arrived a day ahead of the bunch and then received all of us on Sunday morning when we arrived. We had the necessary sets of keys ready for us, and since he lives just across the hallway he was able to help anytime needed (which was a few!)
Some additional considerations worth mentioning are for example the fact that Carlos left 2 SUBE cards at our disposal in the house. If you plan on using public transport, you need one of these cards to top up and travel around with and they aren't apparently that easy to get hold of. We used them, topped them up again and left them for the next visitors.
The flat is comfortable and the balcony is really nice and spacious. Sadly the weather didn't permit us making much use of it, but the interior is really well lit so we could enjoy the outside feeling without the cold.
Modern appliances are provided in the kitchen and the AC system made the place warm and cozy. There's a laundry room with a dryer in the house.
The beds are quite firm and provided with memory foam pillows as well as normal pillows. Also bed linens and fluffy towels are provided. The place has 4 single beds, 2 in each room.
The area is pretty noisy but that's something you should expect in any Buenos Aires area that's near a hub of public transport. It is not the most attractive part of town but it is certainly within easy access to Palermo Soho and Palermo Hollywood areas (recommended for dining and drinks) as well as underground to attend most tourist attractions.
Overall it was a great place to stay and I will use it in my next visit!