For a custom post type named 'listings'

Adding New Content Editor Areas in WordPress Admin

add_action( 'edit_form_after_editor', 'my_new_content_areas' );
add_action( 'save_post', 'save_my_new_content_areas', 10, 2 );

function my_new_content_areas()
{
    global $post;
    if( 'listings' != $post->post_type )
        return;

    $editor1 = get_post_meta( $post->ID, 'my_new_editor_1', true);
    $editor2 = get_post_meta( $post->ID, 'my_new_editor_2', true);

    wp_nonce_field( plugin_basename( __FILE__ ), 'my_new_content_areas_nonce' );
    
    echo '<h2>My New Editor 1</h2>';
    echo wp_editor( $editor1, 'my_new_editor_1', array( 'textarea_name' => 'my_new_editor_1' ) );
    
    echo '<h2>My New Editor 2</h2>';
    echo wp_editor( $editor2, 'my_new_editor_2', array( 'textarea_name' => 'my_new_editor_2' ) );
}

function save_my_new_content_areas( $post_id, $post_object )
{
    if( !isset( $post_object->post_type ) || 'listings' != $post_object->post_type )
        return;

    if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) 
        return;

    if ( !isset( $_POST['my_new_content_areas_nonce'] ) || !wp_verify_nonce( $_POST['my_new_content_areas_nonce'], plugin_basename( __FILE__ ) ) )
        return;

    if ( isset( $_POST['my_new_editor_1'] )  )
        update_post_meta( $post_id, 'my_new_editor_1', $_POST['my_new_editor_1'] );

    if ( isset( $_POST['my_new_editor_2'] )  )
        update_post_meta( $post_id, 'my_new_editor_2', $_POST['my_new_editor_2'] );
}