One man who replied to the bogus ad was found dead in Noble County last week. Another said he escaped after being shot on Nov. 6.
The son of the missing man, Timothy Kern, said his father had been murdered. Kern had called the job offer "strange" in a Facebook post.
Two people are in custody, but law enforcement officials have released few details because of a gag order. Before a judge issued a gag order, the Noble County sheriff said it was unclear how long the ad had been online or whether there were other victims.
Kern was promised $300 a week, a trailer and a truck for the job near Caldwell, his father, Jack Kern, of Massillon, told The Associated Press on Tuesday. He said his son was excited about the job because of the chance of bettering his life.
In a Facebook post on Nov. 10, Tim Kern, 47, wrote: "Just got one of the strangest job offers. A good offer but strange. The job is to watch over 680 acres south of cambridge. Odd jobs and such but mainly just secure it. Trailer, utilities, salary. Drawbacks? No cell phone service, kids are up here, and i have to move this sunday."
Jack Kern said his son was rarely out of touch and often texted and called family members.
"We're holding hope, but pretty grim, I think," he said.
The man who escaped Nov. 6 gave police a similar account of a farm job, saying he was going to build fences. Neighbors near the property where the man escaped said there is no such farm.
The FBI on Tuesday had said Kern's disappearance might be linked to the farm-job robbery scheme.
"We have concerns that there might be a relationship of the case that is unfolding down south," Scott Wilson said.
Before the gag order was imposed, Sheriff Stephen Hannum said that a man from South Carolina who answered the ad was taken Nov. 6 to the desolate area, where he managed to deflect a gun cocked at the back of his head and ran. Wounded in the arm, he hid in the woods for hours, then showed up covered in blood at the first well-lighted place he could see, a farmhouse outside Caldwell, about 80 miles east of Columbus.
Last week, cadaver dogs were brought in, and authorities found one hand-dug grave they believe was intended for the South Carolina man and a second grave that held the body of a Florida man. Investigators have not disclosed the cause of the Florida man's death.