The billionaire second-term mayor of New York got his start at Salomon Brothers investment bank, where he rose from stock trader to partner. In 1981, after being laid off, he founded Bloomberg LP, which has grown to become the largest financial news and data services company in the world. All the buzz surrounding Mayor Mike these days is about a possible third-party presidential bid. If Bloomberg does enter the race, funding won't be a problem -- his net worth is estimated at $5.5 billion.