It might actually be
possible to keep the cost of buying to about six percent if you cut out the real estate agent and buy directly from the owner.
I know an expat who has both bought and sold properties on this site:
https://www.soloduenos.com
You can also avoid the monthly espenses del consorcio if you buy a PH.
You can use use the filters on sites like zonaprop and argenprop (among others) to find listings for sale by owners as well as PH apartments for sale.
Steve is correct- IF you can afford to take several, possibly up to six months, to search, make offers, and go thru with the purchase. And, of course, you must be living here full time during those six months. Which costs something. If you have family here you can stay with, while you search, this could work. Personally, I consider taking that kind of time to save money to be a cost, in and of itself- but I still work for a living, so my time has some value. (sometimes not much, but still).
However, if you are retired, and your number one goal is to save money, and you are willing to compromise on time, location, and quality of the building, you could certainly save a bunch of money.
PH will save you espenses, yes. It will also mean you are solely responsible for building repairs and improvements.
Again, its a tradeoff.
In my building of five units, we all share the inevitable repairs of facades, public spaces, elevators, 100 year old electrical systems, etc, which are then amortized over the year, since the administrator is making time payments to the contractors.
Most likely, this is going to be much bigger amounts, with shorter times to pay, if you, alone, need to pay for a new roof or a new electrical service, or Metrogas decides you need all new gas plumbing from the meter onwards. (which happens regularly in older buildings)
You pays your money, you takes your chances, and your personal appetite for risk, and balance between paying money versus doing research and work yourself, must be taken into consideration.
The procedures, and laws, regarding buying property here are ever changing- just learning what is actually applicable in 2018 will be an education in itself.