I agree with the suggestion of a topic dedicated to residency, it is a major issue and lots of people search for information, including on this site.
For those who are retired, there is a booklet called ´Informacion sobre radicacion por pensionado´ available at the Inmigraciones in Retiro. I didn´t ever find this on the internet (I found various info on the website, some of it conflicting).
In the booklet, it says what you need to do. I don´t want to type it all out here but if somone wants to know, you can give me a call anytime. As far as the apostillation (sp!) goes, it says in the booklet that you that all documentation made by an overseas authority must be stamped by the Argentine consular in the country and ´legalizada´by the Ministry of External Relations, International Trade and Culture. Or, if the country is a signatory to the Hague Convention, it should be apostillado at the Arg Consular in the country. I´m a bit fed up about this as I asked the Arg Embassy in Paris to apostillar a document for me (Certificado de antecedentes penales from the French Govt) and they told me that this was not necessary, no point going to see them. Well, next visit to Paris I will go to see them and will insist that they stamp the paperwork.
The booklet contains a list of the items that you need. I go it just last week, so I suppose it is up to date.
It doesn´t say anything about the minimum amount of pension that you have to receive (typical, they always save something for later...).
In fairness to Argentina, I can say that I was in the queue to emigrate from Australia to Canada for 4 years, while working for the Canadian government in Ottawa. After numerous to´s and fro´s and paying about $2000 I got fed up and moved on. My son´s girlfriend, from India, is having a terrific time trying to get permanent residence in Australia, despite having a PhD iin biotechnology from the ANU and very good career prospects.
Conclusion : migration, no matter where, is not quick or easy.
I hope that this might be useful to someone.
Cheers, Sarah