Before it was a movie and certainly before it was a song, "Leaving Las Vegas" was a novel written by the late John O'Brian.  The book details it's alcoholic protagonist, Ben, and his slow but sure suicide by drink.  Ben goes to Las Vegas to escape, "the frozen tundra of two to six" in reference to the California state liquor laws, and it in Sin City that he meets a prostitute, Sera "with an E."  They form a partnership based on the agreement that she will never ask him to stop drinking and she is ok with that. 

The "Leaving" of Las Vegas is an obvious death reference. 

For the record, the film version of this book was one of those rare instances when a film almost captures the aura of the book on which it was based. 

Here are some choice excerpts from O'Brians' last novel

The first concern's Ben and his self appraisal...

"At times like this he likes to think of his life as one big piece of performance art.  Not structured enough to be an actual play, it is full of irrationality and minuscule details and can only be viewed from the inside out.  Once.  By him.  If he doesn't black out.  He titles this episode:  Pinching pennies and prostitutes-frugal fucking in LA"

Next we have Sera's occupational overview...

"They squeeze their life into her, all they are, all they don't even know about themselves.  Their biology stands at the helm of their bodies.  that's a real fact, true on any level.  Then and there, absolutely, though perhaps exclusively, she has value."

Ben attempts to eat but...

"A protest begins in his outraged stomach."

Lastly, Ben's legacy

"Maybe an overpriced hooker would be a good choice, someone to accept his last blast of semen, his final genetic statement.  Too well paid to douche in his hotel room, the girl would leave with soggy underpants and shower at home.  Hours later, the last of his DNA-possibly surviving him-would be wiped off the back seat of a cab with a paper towel."