Is it permissible to give part of the funds collected for one beneficiary to another beneficiary, and to give the remaining part to a sick person?

The ruling is based on the intention of the donors. If they intended to build a house specifically for the man, then it is not permissible to dispose of the surplus except with their permission. However, if they intended general spending on the needy, then it is permissible to disburse the surplus money to the needy in general, such as a financially distressed person in need of marriage or medical treatment.