Fireman was born to a Jewish family and raised in Brockton, Massachusetts where he attended Boston University, but did not graduate. After working in a variety of jobs, including for a family-owned sporting goods store, Fireman acquired the North American sales rights to Reebok in 1979. He later bought the British-based parent company in 1984. Capitalizing on the increasing popularity of aerobics, particularly with women, Fireman grew the company and issued an IPO in 1985. By visiting gyms and high schools across the country, Fireman conducted first-hand market research. After the IPO, Fireman alternated between building a real estate empire and serving as the CEO of Reebok. Fireman sold Reebok to Adidas in 2006 for $3.8 billion; Fireman himself made $800 million from the deal. In 2009, Fireman founded Fireman Capital Partners, an investment firm. Fireman Capital has bought major stakes in Newton Running, Hudson Jeans, and Evolution Fresh.

Fireman paid $9 million at auction to buy Willowbend Golf Club, which he opened in 1992. Fireman later opened several other golf clubs in Puerto Rico and several states. In 2006, Fireman opened up the $250 million Liberty National Golf Club, which sits on a former Jersey City dump site. In 2014, Fireman proposed a $4.6 billion dollar project on New Jersey's Gold Coast, which would include a 95-story tower with a casino and 100,000-seat motor sport stadium. The New Jersey Constitution does not allow casinos outside of Atlantic City, but Fireman has advocated holding a referendum to change the constitution.

In 2010, Fireman placed his Winecup-Gamble Ranch up for sale for $50 million.

Fireman donated $250,000 to Republican Mitt Romney's 2012 presidential campaign, but Fireman has also donated to Democratic Senators Bob Menendez and Cory Booker and several other candidate and committees of both parties. Fireman donated $1 million to the 2016 presidential campaign of New Jersey Governor Chris Christie.

In 2016, Firemen was an important backer of Public Question 1, a ballot measure that would amend New Jersey's constitution to allow casino Gambling in North Jersey. After numerous polls showed that Question 1 had no chance to pass Fireman, along with Jeff Gural, pulled their financial support for the measure. Bill Cortese, the leader of Trenton’s Bad Bet, a group opposed to the question, said, “Trenton’s Bad Bet will not be distracted by Billionaire developers throwing temper tantrums because they don’t get what they want.”