Boating the length of the Amazon is a big dream but it just occurred to me that it might not be that difficult. There is a public passenger boat that travels from Leticia to Manaus in four days. That is half the entire distance to the sea. While the cost of a voyage on this boat is reasonable (I've heard about US$100) it doesn't seem the most pleasant way to travel (24/7 in a hammock watching people drink beer all day and throw the cans overboard).
Instead, I would like to buy a small river boat in Leticia, and with a few friends, spend a month or more traveling slowly down the river, stopping in the towns and settlements along the way making rest stops, refueling, buying supplies and water, and continuing.
The total distance is about 3000km:

What does one need to consider for such a journey?