[ubuntu] Multiple Users on one Ubuntu installation

I wonder if it is possible to have multiple users using the same computer with ubuntu installed? I would also like to allow users to access that computer remotely by a secure way(should I use VNC or something else?).

Requirements:
-They need to use the Unity graphical interface, not command line.
-When a user reaches the computer from a remote access connection, the system automatically creates an account for him and logs him into the unity desktop
-When the user logs out the computer, the system automatically deletes his account from the system.

Thanks!