Travel around south America on a Motorcycle

This would be long and difficult and I have no idea how to go about it so I could really use some advice on this one. I know it’s become a kind of iconic thing to do. Where do you pick up the motorcycle and what do you do with it when you’re finished. I don’t know how many countries I could hit and I’m concerned about safety in some of these countries. It is something I’d like to try nevertheless even if I only make it through a few countries. This is a long term goal because it requires getting a motorcycle licence and enough money to buy a reliable touring bike down there and I have no money. Potential travel companions are welcome.