Nick went to high school, went to college, got married, worked at well-known companies in Minnesota, and went to law school there. Makes sense to stay in MN.
Weird to live in bumfuck (Minneapolis-commutable suburbs are an hour-and-a-half from spicer/willmar, and even St. Cloud would have been a better place to start a law career - it's an hour from spicer - they could have lived halfway in between the two), but I assume they decided on and never reconsidered being 10 minutes from grandparents.
I just searched Zillow recent sales and found 31 houses in fucking Spicer priced higher than Nick's big house is valued today - he's hardly the "one rich guy" in town. He's not even on water.
And for value, he could have been near St. Cloud or in a Minneapolis exurb or certain suburbs (even very nice ones) for the same money.