I stayed in Martín's apartment for two months and enjoyed it a lot. Check in and check out are super convenient and he was always reachable in case of questions. The location of the flat is excellent to get to know Buenos Aires and everything you need is close by (bakery opposite of the apartment, a lavanderia on the same block etc.). The apartment has everything you need, also for longer stays. It can get a bit loud sometimes during the night, but you are in the center of Buenos Aires, after all.
Muchas gracias Martín, hasta luego!