Well, there is a lot of misunderstood about how to probe you full fit the requirement for rentista visa. The big issue is that the immigration agents have very low knowledge about law and it´s interpretation. Last time I was there I had to be very nasty and said, why should I be talking with you if you are not a lawyer. He understood and toke my papers.
The idea behind the rentista temporary residence (this is not a visa, please) is that you don´t need to work for living in Argentina. This is what you have to probe.
The fisrt option the law has is that you live from your savings. Of course the stupid immigration agents will tell you you must have a house abroad, to rent it and receive this money here. This is the second option but they believe the only one. For this reason is better to do the apply with a lawyer.
So, the irrevocable trust in monthly basis is not necessary. If you have savings this is enough.
Please, don´t complain about burocracy, we have the most open migration policy, if somebody wants to live in the state has to be illegal or to marry somebody. And in Europe, to invent a european grandfather.
Ok, about new requirements. 2000 u$s and you have to probe they come from legals activities. This is new and is related to decreto 616-2010 (this is an administrative law that "translates" the migration law). This new law is brand new, from 7.7.2010. You tax papers should be enough to probe that this money didn´t come under the table.
The decreto 616-2010 is all about more control, police powers to migration agents (now they can double check the info you provide, they can go to your places, etc) and deportation.
So, I suggest to abandon the idea about going to Colonia for ever and start applying for temporary residences. This new law specifies you can go and back to a place like Colonia once and after that they must deport you. Before this it was up the agent at Customs. So, it will take some time for them to organize it, but the situation has changed.
http://www.unhcr.org/cgi-bin/texis/vtx/refworld/rwmain?docid=4be2de512
Regards