In his decade of working construction and home remodeling, David Gonzalez always dreamed of finding some hidden treasure in the demolition work. He’d even put dollar bills in new walls for folks to unearth in the future.

So he chalks up to karma the 1938 Action Comics #1 book he found amid old newspapers used to insulate a wall of a fixer-upper he was gutting in Elbow Lake, Minn. The old comic book, from June 1938, features a new character named Superman lifting a car on its cover.

“I knew it was worth money,” said Gonzalez, 34. “But I had no idea how much.”

He’s quickly finding out as he sells the comic book in an online auction that runs until June 11. It has already attracted 31 bids, including one for $107,333, in the first two days of the auction.

The comic could have been worth more had it not been for a heated argument with one of his in-laws.

When his wife’s aunt grabbed the comic book amid all the excitement of the discovery, he grabbed it back and tore the back cover. Experts downgraded the comic book’s condition to a 1.5 on a 10-point scale. To put that in comic-book context, a 9.0-grade Action 1 fetched more than $2 million recently.

“That was a $75,000 tear,” said Stephen Fishler, co-owner of ComicConnect, a New York City online auction house that is selling Gonzalez’s treasure. He says the comic book would have graded out at 3.0 without the rip.

Even so, comic book collectors are amazed by Gonzalez’s find. Most of the Action 1 comic books out there have been traded and resold many times.

“This is like a virgin comic in this instance,” said Vincent Zurzolo, a co-owner of ComicConnect.

“It’s so hard for anyone to fathom that, in this day and age, you could still discover a comic book that nobody has known about because this book was in a wall of a house for more than 70 years,” he said. “It’s pretty miraculous that it even survived and it’s only had one owner.”

Gonzalez said he has no regrets about the argument that damaged his discovery.

“I am a humble working guy, so I didn’t get too excited when I found it with old newspapers stuffed in the walls,” said Gonzalez, a father of four. “Money won’t buy you happiness.”

His in-laws didn’t have the same reaction.

“They got all excited and tried to take it,” he said. “I understand it’s something cool, but told them: ‘You don’t have to act so rude. I brought you in to show you, don’t grab it.’ ”

Still, it’s going for more than 10 times what Gonzalez paid for the abandoned house in Elbow Lake, about 160 miles northwest of the Twin Cities. Gonzalez lives in Hoffman, near Alexandria, and spotted the house with a torn-up roof last winter.

He and his wife went to the Grant County courthouse and researched the owner, who told them a neighboring restaurant had offered $10,000 to buy it. They planned to demolish the house and put in a parking lot.

“So I offered $100 more and got it for $10,100,” he said.

Little did he know, that price included Superman, circa 1938. He has since driven the comic book down to Tampa, Fla., where a dealer serves as the middle man with the New York online auctioneer. Gonzalez says he’ll get half the final sale price, prompting a chuckle from his wife.

“I didn’t think anything of it,” Deanna Gonzalez said. “It’s just a comic book.”