The preparation of such a trip has comforted us in the idea that, although we are far from being the first to do it, it remains rare. Therefore it arises the curiosity of many and can be seen as an opportunity to try to take advantage from it: negotiating discounts, partnerships etc…
Along the long preparation process many idea come to mind and it is good to pay attention to them. this is how we ended up taking first-aid classes or undertaking serious physical exams (we are not 22 anymore!)
But more seriously the following points are important. So this might help:
No need for visas (for French people) for the countries we go through (Argentina, Chile, Bolivia, Peru, Ecuador and Colombia). But exchanging with the authorities (consulates) has been reassuring.
For example we learnt that the rumor saying that you NEED to show a return ticket when entering a country is just a rumor. it is NOT compulsory for these 6 countries.
It is important to go and check this point early enough because some vaccines need several injections to come to full effect (rage for example).