Buenos Aires Travel Rent (BATR)
Just a note of caution if renting from BATR. They do not proprate the rent for an apartment if you are staying for a long term. In other words if the rent is $1000 a month but $300 for a week and you are staying 6 weeks, they will charge you $1600 rather then giving you the monthly rate for the 5th and 6th week. I tried to negotiate this but they refused.
I did discover the same apartment for rent through BYT and in that case they prorated the rent. Same apartment, same dates, but a very different price.