Is it permissible to collect Zakat funds to help an elderly, incapacitated cousin with a large family who wishes to build a house on land granted to him by the state?

It is not permissible to collect Zakat for a Muslim to the extent that it suffices him to build land if he already has sufficient housing, because Zakat is for the poor and the needy who require food and drink, not for owning homes or land. If he does not own a residence, a dwelling can be rented for him from Zakat funds if he is unable to pay the rent.