You don't have to be a resident to buy real estate here, all you need is a local tax ID number called CDI (see our Weblinks->Real Estate->AFIP guide). And you can just stop by at the tax office and get it. You need to show your passport and (please, correct me if I am wrong) a proof of an address. I believe I had to show a cable bill on my name or something.
Yes, rip offs are quite common. Even an established real estate agency can try to sell you an apartment with a bank lien against it. As an absolute minimum you should never accept a notary whom real estate agent suggests. Try to find someone who is independent and cares about his reputation. It is highly recommended to hire your own lawyer as well to oversee the transaction.
Expect everything to be slow and painful

. If people say that it takes a 3 days to get, say, proof of an ownership from the real estate registry, it may take a month easily. You should be ready that situation can take an unexpected twist at any moment. Even after the money transferred hands you can hear something like "Oh, and by the way, current owner will stay there for a couple more weeks". So, the whole experience may be quite stressful.