There are two types of rentals in Argentina. There are the temporary, furnished apartments, which are short term. And then there are the normal, two year contract to rent an unfurnished house or apartment. To get a 2 year contact, you will have to be able to get a garantia, which is basically a person who agrees, in contract, to pay the rent if you for some reason are unable to. That person has to own property, and at least in Capital, they need to have the same last name as you. But the specifics of the garantia will depend on the agency you rent the apartment from.
Since you mentioned that the company will be helping you move, the best thing you could do is try to see if they will rent a property for you.
Belgrano is very safe and there are a lot of families that live there. Personally, I find it to be much safer then Recoleta. In the suburbs, Vicente Lopez, Olivos, La Lucila, and Martinez are all fairly safe. There are more house than buildings and the areas are some of the wealthiest near the city.