When will it be profitable to mine the moon of Helium 3 ?

A long, long, long time from now, when we have some sort of very advanced propulsion system that uses barely any fuel, but also is decently fast enough with a large load. It will also need to be for something used in orbit as getting large amounts to earth would be very difficult.

It isn’t as hard as @XOIIO speculates, since getting into space from the moon doesn’t require the propulsion that it does from Earth.
The movie Moon isn’t far off how it will be done.

Never. It isn’t cost effective.

What can you do with it?

@antimatter I believe you can use it as a fuel source.

O… well than it would be cool to mine the moon