When does a man become a Christian?.....

It works out like this:
The man may have a different faith, or no faith at all.
The message of the Lord reaches the man and he listens.

This message sinks down into him about the death and resurrection of Jesus Christ and what that means to people...

He believes in the resurrection....
Now in that moment he believes, at that instant, at that single heartbeat...... he is a Christian.

and yes, it may take the whole rest of his life to conform his life to the image of Christ.
But he is truly a Believer, he is truly a Christian, he is truly now and forever more, "saved".....

it's that easy to become a Christian.