[Answered ]-Getting started with Django on Virtualbox>Vagrant>Ubuntu. Can't run django-admin

You haven’t done step 4. You have not installed Django, let alone within a virtualenv; all you’ve done is clone the Django repo, which is unnecessary.

For step 4, you need to create a virtualenv, activate it, and install Django inside it using pip.

virtualenv my_django_proj
cd my_django_proj
source bin/activate
pip install django

Now, django-admin startproject mysite will work.