The ‘Patient Zero’ artist bought the multimillion-dollar beachfront retreat at just 23 years old.Credit: Getty Images / InStyleThe GistTaylor Swift owns a $17.75 million Rhode Island mansion known as ‘High Watch’ or ‘Holiday House.’ The coastal retreat was once the site of the singer’s famous Fourth of July parties, attended by her squad of celebrity friends.Holiday House’s history inspired her 2020 Folklore song, “The Last Great American Dynast…