Key Biscayne mansion listed for $60M sale – South Florida Business Journal Posted by 305SocialMedia.com | Sep 11, 2014 | Business | 0 | The 5-story, 11,600-square-foot mansion was built in 1991. If sold at $60 million, it will break the Miami-Dade County record for home sales, which sits at $47 million. Source: www.bizjournals.com