A massive land parcel south of Kissimmee is for sale. The historic Green Island Ranch, a 5,977-acre parcel in Osceola County, is listed for $140 million — or $23,423 an acre. The land is entitled for mixed-use development for up to 17,000 residential units. The property is listed by Lakeland-based SVN|Saunders Ralston Dantzler’s Dean Saunders and Dusty Calderon, the latter …