I should mention that while Les Baxter's instrumental version of Marguerite Monnot's song is the most popular American version, the "Poor People of Paris" is a jocular mistranslation (by Jack Lawrence) of a French song.
The French song, "La goualante du pauvre Jean" (The ballad of poor John) has lyrics by René Rouzaud and is one of the signature songs of Edith Piaf. Try http://www.google.com/search?q=%22goualante+du+pauvre+jean%22 for more. It's hard to get a good translation because of the old-fashioned slang, so here's my best shot at cracking the idioms.
To the ballad of poor John
Whom the women didn't love
But don't forget
Life has just one moral:
Whether you're rich or broke
Without love you're nothing.
He lived from day to day
In silk and velvet.
He slept in finest linens
But don't forget
Your life's an empty shell
When your heart is in hock.
Without love you're nothing.
He lunched with tycoons,
He boogied in the salons
And guzzled all the brandy,
But don't forget
Nothing is worth a beautiful girl
Who shares your soup.
Without love you're nothing.
To get his cash
He became a cruel thief.
People bowed way down before him
But don't forget
Some day you'll get arrested
And behind prison bars
Without love you're nothing.
Listen well, you younger folks,
Make your twenty years count
You only get them once
And don't forget
The woman is worth more than
A string around her neck.
Without love you're nothing.
And there you have it, my good folks,
The ballad of poor John
Who says to you in parting
Love! (Ba-doop-a-doop-ba!)
I'm still a little unsure of the bit about the string around her neck; my best guess is that it refers to a valuable necklace, perhaps a string of pearls.