Steven Cross, 60, who has had sole custody of his son since the boy was 1, said in his note he was about to lose the Lakeville, Minn., house where they lived to foreclosure and that the boy's mother was still alive, not dead, as the son long believed, ABC reported.
"If this paper is wet, it's because I'm crying so bad," the architect's note said. "You know your dad loves you more than anything....There are no jobs for architects so I have to go because the sheriff will take the house July 27th."
Police arrested Cross Monday in Cambria, Calif., as he headed to a deli where he had found a job.
He waived his extradition to Minnesota in a San Luis Obispo County court Wednesday, but is expected to return there within two weeks and faces a gross misdemeanor charge of child neglect, ABC said.
The boy, who ABC did not identify because he is a minor, heeded his father's instructions and went to a neighbor's house. He was staying with a relative while child-protective service officials determine who will get custody.
The boy's mother, Katik Kristina Porter, 38, contacted authorities this week.
"There are many great years ahead for you. Not so for me," Cross wrote to the boy.