What's "The first thing you know"?

Old Jed's a millionaire.

Naw, the the next thing you know.

Your mother's voice

No, Tyler's right!

I like Lou's answer more, but Google never lies.

Actually, Tyler was right, my bad:

Come and listen to a story about a man named Jed
A poor mountaineer, barely kept his family fed,
Then one day he was shootin at some food,
And up through the ground came a bubblin crude.

Oil that is, black gold, Texas tea.

Well the first thing you know ol Jed's a millionaire,
Kinfolk said "Jed move away from there"
Said "Californy is the place you ought to be"
So they loaded up the truck and moved to Beverly.

Hills, that is. Swimmin pools, movie stars.


Well now its time to say good by to Jed and all his kin.
And they would like to thank you folks fer kindly droppin in.
You're all invited back a gain to this locality
To have a heapin helpin of their hospitality

Hillybilly that is. Set a spell, Take your shoes off.

Y'all come back now, y'hear?.