The Duchy of Cornwall, which is some 135,000 acres within the UK, will pass to William, and he will receive his income from the working estate as Prince of Wales when he assumes the title. https://duchyofcornwall.org/about-the-duchy/
“The Duchy of Cornwall is a private estate established by Edward III in 1337 to provide independence to his son and heir, Prince Edward.”
It also funds the public, charitable, and private activities of the Prince of Wales and his family.