There's the budget aspect too, but likely your company will pay for the rent, did they give you a limit ?
A good house is Olivos, Martinez, San Isidro, furnished, with pool has a r ent of likely 2500 USD minimum for a short term rental (that's my own guess).
A good house in or around Pilar, with a bigger garden and a bigger pool, furnished would be subject to negotiation (they don't appear on the internet, and can be found from word of mouth) but could probably be found for about 1200/1500 USD.
I pay 500 USD + 100 charges for a 2 floors house in a gated community, unfurnished, with 2400 m2 (20.000 sq.ft) and a 10x5 meters pool. The house is not in a perfect shape (a bit of infiltrations) but is nice, and the garden is beautiful.