If you are planning on filming a movie (for theatrical release or for television) or a commercial, one of the key players you will be dealing with is the film crew union, or SICA (Sindicato de la Industria Cinematográfica). Unlike in other Latin American countries, film crew members are not independent contractors: they need to be contracted with a union approved contract and receive the union´s benefit package (which includes health care, social security, and even discounts on vacations). For commercials, day rates apply but for films, salaries are based on weekly rates.
The union can file law suites against production companies that do not follow their guidelines and prohibit commercial releases in Argentina if union wages are not paid. However, unlike the US, a crew can be made up of union and non-union members, and membership in the union is optional.
One reason many foreign film companies hire local fixers is that if facilitates dealing with the union: as you can see from their website, they don´t speak English!
Filming in Argentina: The blog of San Telmo Productions 