Conlon was born in Birmingham, England to Irish parents and was raised in Rathangan, County Kildare, Ireland. Before immigrating to America in 1990, Conlon attended the College of Marketing and Design Dublin Institute of Technology in Dublin, Ireland and worked as a credit analyst for Lehman Brothers in London.
In 1993, he joined Koenig & Strey and within a few years, Sean became recognized as one of the leading sellers of residential real estate in the US, while still only in his 20's. Sean set yearly sales records nationally among real estate agents that exceeded $150 million.
Conlon made his name buying small homes and replacing them with three-story condominiums and single family homes. Previously in Chicago, builders created developments and brought them to estate agents who sold them, but Conlon devised a new formula where he found the land, architect, builders and then marketed the entire project.
In January 2000, Conlon formed Sussex & Reilly ("Sussex"), an Illinois-based real estate brokerage firm. The firm began with a 10-person staff and quickly became a major player in Chicago residential real estate. Sussex grew to over 300 employees and annual brokerage sales volume in excess of $1 billion, Sean subsequently sold Sussex in 2006. Also in 2000, Conlon started Conlon & Co: A Real Estate Merchant Bank to provide real estate consulting and financial services to clients in the industry. Conlon & Co consults to funds, institutions and high-net-worth individuals, providing these clients with advice, asset evaluation, acquisition support and portfolio management.
Since 2002 Conlon has been a partner of Van & Conlon, which has built developed 100 vacation homes. In 2004, in partnership, he acquired Near North National Title ("Near North"). Established in 1988, Near North handles up to $5 billion in real estate transactions annually across the US. He sold Near North in February 2010. In 2005, Sean launched Connaught Real Estate Finance, a $100 million mezzanine fund that lends money to developers. In 2007, he started Conlon & Co | Europe with an office in Dublin that advises European investors placing money in American projects.
In 2009 Conlon returned to residential real estate brokerage. In June 2013, CONLON became affiliated with one of the world’s real estate networks, Christie’s International Real Estate. Christie's is one of the oldest privately held brands in the world. Their International Real Estate division specializes in high-end properties and has offices worldwide, including London, Sydney, Italy, New York and Hong Kong, and Chicago. CONLON is the Christie’s exclusive affiliate in Chicago.
In 2017, he launched Conlon Capital, which focuses on commercial real estate lending,
In November 2016, CNBC announced that Sean would be the co-host of its newest show The Deed which premiered in March 2017. "The eight-episode one-hour series will follow Torres in New Orleans and Conlon in Chicago as they throw distressed developers a lifeline by offering them their own cash and expertise in exchange for a piece of the property and a percentage of the profits."
The first of four episodes of The Deed: Chicago premiered on March 29, 2017 with subsequent episodes on the three following Wednesdays. the show consistently ranked in Showbuzzdaily's Top 150 Original Cable Telecasts and rated as high as the top 15 for its timeslot.
In August 2017, CNBC announced that The Deed: Chicago was being renewed for a second season to air in 2018