Okay, look, this isn't hard, people. I found this one in the DT just by searching for "sun shine back door":

THAT'S WHY I'M WALKIN'

My boss-man was so mean, I works just like a slave
16 long hours drive you to your grave
That's why I'm walkin, walkin my blues away
You know the sun gonna shine in my back door some day.

I once had a car, it were painted white and black
Couldn't keep up the payments, the man he took it back,
That's why I'm walkin, walkin my blues away (hey, hey, hey)
You know the sun gonna shine in my back door some day.

I wouldn't tell a mule to off if he sat down in my lap
Ain't that the same thing killed my old gran-pap?
That's why I'm walkin, walkin my blues away
You know the sun gonna shine in my back door some day.

Performed by Sonny Terry and Brownie McGhee
(Fantasy Records: ""Goin Back to New Orleans"" 2-record set)

---------

Alex