Hi
We use Reynolds Properties. They allow a deposit of 10% by visa, which is non refundable, but a lot safer than handing over money to someone you don't know. Remember the first rule of Western Union - never send money to someone you don't know. We still have to pay the similar damage deposit.
We wanted to rent for six months, but were not prepared to pay up front, so only rented it for two months at a time. One difference is that we stayed at the place for 4 months last year so it was like coming home.
I find the other difference is if the owner is Argentine or a foreigner. Because the NZ owners of our apartment can't do anything, Reynolds takes care of things, while other people renting from them have to deal with local landlords for any problems and then the response is mixed - from excellent to poor. , Some of it is the luck of the draw. Still, all the people at Reynolds speak English and do have an attitude of wanting to help.