In 1920, Ole is living in Fillmore County, MN, living as a boarder with a George Nelson family. when he registered for the World War 1 draft two years earlier, he was living in Spring Valley, MN, and Charley Rustad was living in nearby Ostrander, MN.

Charles is listed as "cousin" to Ole Rustad in 1930 Aitkin County, MN. Ole owned his own farm, was single, and it was the depression. The first thing that comes to my mind is that Ole needed help on the farm and his cousin (possibly out of work) came to live with him.

I don't find any articles in online sites pertaining to your Charles / Charley / Carl Rustad