Longboat Key, FL Real Estate and Homes for Sale. Looking to buy a house? Weâve started the research for you and hereâs what you need to know about Longboat Key. Longboat Key, located in Sarasota County, Florida, is home to 6,930 people and is a suburban community. The median household income is $98,899. 73% of residents of Longboat Key are married and 4% are families with children.