Hello,
I don't know a lot about the cost of living in BA but I have my personal experience for a middle class living. Coming from abroad you may have more wealth and could go a little higger, anyway, I think my experience may be good as a sample of how to live well with minimun expences
I'm renting a 48m2 department for 1000 pesos every month, I have low mantaeinance in the building becaus it has no elevator and no other fascilities. It is located in Almagro, which is a god location, is close to the subway and many bus lines.
So I calculate you can live very confortable for just 3000 pesos every month. If you have more then you can think about rising your level and going for a bigger department or to a more exclusive zone like Palermo o Recoleta (I don't know how much this can cost but I'm sure that someone here will tell you).
I hope you find this information useful.