Buenos Aires, in my opinion, and I'm no fan, is no more dangerous for an intelligent watchful person than any other large crowded city. People will steal from you if you let them. The worst things I've heard happening to expats here, a man being beaten walking on the street and woman being raped by a taxi driver, both happened because the person was out very late at night and VERY drunk. That is stupid even in Mobile Alabama. If you drink go with friends and don't go home alone. If you are out late, be alert, watchful and careful, take a taxi with a friend and get inside off the street. BA is very much a night city, especially for the young, but there is no one to blame but yourself if you are vulnerable and get hurt. Good advice here all around.
I agree with the man who suggested other places. BsAs is NOT cheap, it's not an easy place to live and frankly Spanish speaking from all over the rest of the world look down on the accents of people from here. Just the other day a repairman said something to me that took me, after 2 years here, a while to understand. He kept saying "mee-shon-ess" and I couldn't grasp it, then in context came to understand he was saying Millones, which of course, any where else in the Spanish speaking world would be pronounced "mee-yon-ess" possibly with a little L sound thrown in between the I and the first L. Learning to speak Spanish in Argentina is like learning to swim in the Sahara. It's possible, but you'd be better off choosing a different spot...