Is it permissible for a master's student who receives a special financial grant to also receive an additional government financial grant and use it to build his future and a home for himself?

If the granting body (the government) does not stipulate that there should be no other granting bodies for the second grant, then there is no objection to accepting it if you meet the conditions. As for disposing of the grant money, the rule is to refer to the condition set by the granting body. If it does not stipulate the return of any excess beyond study needs, then receiving the money constitutes ownership and permits all lawful dispositions of it.