Not used often now, but can mean a number of different things:
1 A person who takes bribes from both sides of a dispute;
2 A double-dealer, crook or cheat;
3 A person able to play (musical instrument or sport) with either hand;
Someone who is addicted to obtaining money and building wealth. A money addict and fanatic. Breadheads often work more than one full-time job, and some even participate in illicit activities to "obtain the bread".