Is it permissible to receive Zakat to help complete the building of a house for a family whose sole provider is the questioner, given his difficult financial circumstances and his family's need to vacate their current dwelling?

There is no harm in giving zakat (definition) to someone who owns land but lacks the funds to build on it, as they fall under the general categories of the poor and the needy. Furthermore, someone who owns a dwelling and furniture but lacks sufficient means is more deserving of zakat than someone who does not possess these essential necessities. Abu Ubayd al-Qasim bin Salam mentioned that if he saw a family of righteous Muslims who were poor and had no dwelling to house them, and he purchased a residence for them from his zakat money, he would be fulfilling his obligation and doing good. Therefore, there is no harm in accepting assistance from colleagues as zakat.