If you arrive with a few months of rent money set aside, you should be fine. Teaching English will support daily expenses (food, entertainment, cell phone), but not daily expenses
plus housing. And
definitely not expenses, housing, plus domestic travel.
Let's do the numbers: assuming you find immediate work with an institute -- at 40 pesos an hour, teaching 20 hours a week, you would receive about AR$3,200 at the end of the month. If a room share costs $400 USD (AR$1,746) per month, that would eat up over half of your monthly salary, leaving you only AR$1,450 to live on for the next 30 days. That's impossible. But taking the housing factor out of the equation, you can get by on AR$3,200 a month.
If you want to start familiarizing yourself with the cost-of-living in peso terms,
www.discovirtual.com.ar and
http://www.buenosairesdelivery.com/ will allow you to see the current prices of groceries and dining out. And
http://www.omnilineas.com/ will give you an idea of what bus tickets cost these days.