Dr. Monzer Kahf, a prominent economist and counsellor states: “For the current year, one will need to include the market value (on the day when Zakah is due) of the commercial land/house purchased for the purpose of selling it because buying it with that intention makes it similar to any item purchased for sale to make profit.
The Zakah is due on the net Zakatable items, that is by deducting the amount of debt one owes other people whether on a particular land or any other debt one may owe regardless of its objective or what was it used for. In other words, one need to estimate the market value of the land/house and include it in the Zakatable items and deduct the debts owed. And we do this on the day of the due Zakah. Additionally, for gold and any other Zakatable item one owns on the due day of Zakah, we use the price that we can get if we sell the item on that day regardless of whether this is below the purchase price or not.“