How to Calculate Zakah on Real Estate

If a man has land or a house that is not for real estate investment or for sale, for example, but he sometimes watches for the price to rise or someone comes who wants to buy the house, and he looks to see if the price has increased or not, and he has no intention of selling it at all, does he have to pay zakah?
If the man is one who buys and sells in real estate, then he has to pay zakah. But if he wants to develop it, for example, and does not intend to trade in it, then there is no zakah on it. However, if he sells it, he pays zakah on its value if the year has completed while he has been in possession of it.