Gear Head, spend some time and search the man. See what you can dig up literally on him. See if he had the means for the money.
Point in case, my Grand Dad was your dictionary example of a "dirt poor farmer". Couple of cows, pigs, and chickens. Never had the equipment to plant or harvest a crop. Did a little butchering for side money, and sold insurance door to door to make ends meet. Drove an older car, seemed he was always wearing the same clothes when I saw him.
As I grew older I learned and was taught a few things. He had "friends", those friends provided the feed for the animals, planted and harvested the crops, and some other things. When Gramps passed I found out my poor Grandfather had, along with the butcher shop and insurance business, had owned a car dealership, had hands in a second, was partner in 2 different motorcycle dealerships, a department store, a furniture store, a heating oil/propane business, had timber/coal/gas contracts, and had more money then God. He had and still has unfound stashes. He grew up in the Depression, and lost money when the bank folded, never trusted them again. There was money found in jars on his workbench, behind the medicine cabinet, under the stairs, in books, under dresser drawers, you name it he hid it there. Not to mention the well, or the spring, or the one in the junk pile behind the house.
Not bad for a poor old dirt farmer.
p.s. just a tip, keep an eye out for the family, they most likely know more then they are saying. And if you, like me, can't prove where the money came from initially, but have a good idea, look out for "friends" of the guy. They may be a good thing or a not so good thing in your search.
Best of luck!