Doesn't do any good to try to arrange anything past Mexico in advance. Visas need to be used quickly, and they're either not required or can be bought at borders or in neighboring capitals. Mexico aside, you can't buy insurance or fill out border paperwork until you arrive at an actual border. Besides, you've got no idea in the world where you're going or when....although this might not be apparent just yet.
The right direction is to either search here exhaustively, lurk here methodically, or (preferably) both. There are no better overlanding sites.
For the very basic overview, check the State Department site, which gives visa requirements for all the countries. However, don't look at the travel advisories or you'll give up, bolt the door and never leave home.
Hope that helps.