Are Freemasons expected to prefer fellow Masons at the expense of others?

Absolutely not. That would be a misuse of membership and subject to Masonic discipline. On his entry into Freemasonry each candidate states unequivocally that he expects no material gain from his membership. At various stages during the ceremonies of his admission and when he is presented with a certificate from Grand Lodge that the admission ceremonies have been completed, he is forcefully reminded that attempts to gain preferment or material gain for himself or others is a misuse of membership which will not be tolerated.

The Book of Constitutions, which every candidate receives, contains strict rules governing abuse of membership which can result in penalties varying from temporary suspension to expulsion.