How old was Tom when his father left and he had to take over the responsibilities of financially supporting his mother and sister?The Glass...

In the beginning of Scene I, Tom as narrator introduces
the characters along with himself.  Pointing to the mantel where a
"larger-than-life-size photograph" hangs, Tom refers to the fifth character, his father,
who was a telephone man.  Tom describes him as a man who "fell in love with long
distances," leaving his job and his home.  All he did was send a postcard from Mazatlan
on the coast of Mexico that read "Hello--Good-bye!" with no return
address.

This photograph of Mr. Wingfield shows a young man
in a World War I cap.  Since the play is set in 1944, the time of the second world war,
the father has obviously been gone for a long time, and was probably rather young when
he left.  However, no mention of the year that he left is made.  Since The
Glass Menagerie has elements of autobiography in it, and Tennessee Williams's
father left his family when Williams was only seven, this age may be the approximate one
for Tom, as well.

Later, in Scene II when Amanda returns
home after discovering that Laura has not been attending Rubicam's Business College, she
bemoans the fact that they will have nothing for the rest of their
lives:

"What
is there left but dependency all our
lives?"

This reflection
suggests that the Wingfields have been dependent for some time, and Amanda worries that
this will continue. Further in this same scene Amanda comes out wearing "a very old
bathrobe...a relic of the faithless Mr. Wingfield," so, again, there is the suggestion
that the father has been absent for a very long time.