WP_cron won’t trigger my action

You need to call add_action from outside the class, with a reference to the object. Example:

$cj = new Cronjobs;
add_action('update_properties_daily', array(&$cj, 'do_updates'));

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)