user has a client who is building a Website in Drupal, and claim that he is unable to export any kind of content files for translation. Can't all the content nodes be exported as XML? Or the translation catalogs as PO files?
indeed a Drupal site must first be enabled for translation. This requires a Drupal web agency and is indeed non-trivial.
Once done, the built-in Drupal tools for translation management will work.