Ivan's apartment is a really great place to stay in BsAs. The location is Central to the subte (San Jose station is 3 blocks away that will get to anywhere in the city, and cheap). Avenida 9 de Julio is also nearby with bus lines that can get to anywhere up need to be. San Telmo market is a 15 minute walk and the Sunday market is wonderful. We stayed in his apartment for nearly 3 months and found it to be a great base. Ivan is kind and responsive and his friend, also named Ivan, is helpful if anything needs fixing.
The upstairs deck area is great for hanging and cooking.
I would recommend Ivan's place. Thanks Ivan!