@danfromisrael this is exactly how you should work on any project. If there is no documentation, start writing at least small notes to yourself. At the end make sure your team contributes and everyone uses it. Problem, however, is that in a typical business you won't have much time for writing good documentation. managers consider it as a time and money waste for company.
At the end when you can choose and your time become expensive you can find a better place/project.