You must be knowing that
according to the established Sunnah of the Prophet (sws) items of personal use
as house, car, etc are exempt from Zakāh. However, if you are yet to make such a
deal and your Zakāh paying date arrives, then you must pay the Zakāh of this
reserved money. The simple reason is that the currency reserved to buy such an
asset is yet to be converted into that asset.