While installing homestead following the official installation instructions of version 4.2, I received the following error message when executing
$ homestead init
Command "init" is not defined.
composer global require "laravel/homestead=~3.0"
Laravel Homestead version 3.0.1
Hmmm I remember having this problem when I was first installing homestead. I can see the link you provided is in relation to Laravel 4.2. Following the homestead installation from the 5.2 docs seemed to be fine for myself however: