Most nationalities do not need an entry permit for Argentina, they receive a free 90 day tourist visa upon arrival. However sometimes some nationalities require entry permits and these have to be bought on the internet before arrival in Argentina. At the moment of writing this includes the USA, Canada and Australia amongst others.

The link for payment is:

And you can find instructions for filling this form in on:

All guests are required to have travel insurance which covers riding activities if they wish to ride. No vaccinations are required for entry to Argentina and Patagonia is a healthy environment. However you should always check with your physician.