David Gonzalez said he purchased the Elbow Lake house for $10,100 and discovered a copy of Action Comics No. 1, a June 1938 comic book featuring the first appearance of Superman, among the old newspapers used to insulate a wall, the Minneapolis Star Tribune reported Wednesday.
Gonzalez said he wasn't quite as careful with the find as he should have been, accidentally tearing the cover and downgrading its condition from a three out of 10 to a 1.5 out of 10.
A copy of Action Comics No. 1 graded nine out of 10 recently sold for more than $2 million.
Gonzalez said he put the comic book up for auction at comicconnect.com, earning a high bid of $107,333 as of Wednesday. The auction ends June 11.