Is Zakat obligatory on a commercial property that has not yet been finished and its purpose has not yet been determined (for personal use or for sale), and if it is obligatory, is it calculated based on the purchase price or the current market price?

There is no zakat on a commercial premise if its owner is not firm in the intention of trade, but rather hesitant between selling it or keeping it. This is because zakat is not obligatory on trade goods unless the intention of trade is confirmed at the time of acquiring them.