I would suggest that if there's any way to purchase the mineral rights, that you do so just in case there's something under there they don't currently know about. My grandpa was smart and purchased the rights because he thought one day there might be oil on the land, and everyone else thought he was dumb for doing it. Turns out all of the nearby ranches didn't have a chance to buy their mineral rights because some investing company did it first, and they lost out on millions of dollars when they started digging for (mining? I don't know what you call it) natural gas in the area.