It is really hard to get a feel for big numbers, but important to try.
In terms of "buy everyone a house". What could William do?
Well according to a random website, he has a personal wealth of about £100 million, and controls the Duchy of Cornwall worth about £1 billion. If we combine that with all the other assets controlled by the Crown or the Royal Family, then that is more or less £30 billion.
Now suppose he decided to give absolutely all of that to "everyone". So he liquidates the lot, sells off all the palaces, all the land, all the businesses and shares out the proceeds evenly.
(This rather begs the question as to who could afford to buy it all, but let's ignore that for now.)
How much would this windfall be?
£30 billion, divided by £70 million people is a smidge under £430 each.
So no. Even in the most extreme case, where nothing is left of the Crown's fortune, William could not get remotely close to buying everyone a house. Maybe, just about, if he held on to one of the larger, cheaper estates, there would be enough left to give everyone a small plot of land and a cheap garden shed.
William is rich, very rich. But not even close to "resolve the country's problems" rich.