A completely, 100%, forever, all the way, original joke. By me.

So this unemployed engineer decides to open up a holistic healing center.

Puts out a sign saying:

"Holistic remedies guaranteed to cure any ailment for $500; we'll pay you $1,000 if it ain't."

A crazy bum thinks this is a good opportunity to earn $1,000 and goes inside.

Bum: "Gimme some gasoline."

Engineer: "Somebody get this man some gasoline."

Bum: "Thanks!"

Engineer: "You didn't ask to treat anything. So, please leave."

The Bum gets delirious from all the gasoline he downed and goes back after a couple of days later for more gasoline.

Bum: "I have lost my memory."

Engineer: "Get this kind man more gasoline."

Doctor: "Yay! More gasoline!"

Engineer: "That's right!"

The Bum leaves happily and comes back after several days, more determined than ever to get more gasoline.

Bum: "My eyesight has become weak."

Engineer: "What is this joke about again?"

Doctor: "Gimme $500..."

Engineer: "Here's $500 worth of gasoline."

Bum: "Thanks!"

The engineer goes bankrupt from all the free gasoline he gave away. Later in life he starts another clinic and rips off some doctor. The bum dies from all the gasoline he drank.