Add note RE differing pip versions

README.md

@@ -20,12 +20,14 @@ Using a virtual environment is very important for ensuring that all work is done
 
 `brew install pipenv`
 
-*Note: Mac users can also install through pip, but using Homebrew is recommended.*
+*Note: Mac users can also install through Pip, but using Homebrew is recommended.*
 
 #### Other systems
 
 `pip install --user pipenv`
 
+*Note: You may have versions of Pip installed for both Python 2 and 3. If so, your Python 3 Pip will be called pip3. Check if this is the case by running `pip --version` and `pip3 --version`.*
+
 ### First time package install
 
 Run `pipenv install` in the project's main directory.