In terms of monetary value.
Depends on your field and what you want to do with it. A management consultant might win a lucrative assignment to France or Germany because he knows the language; a public figure might get a great ambassador position in Iran or Turkey because she knows the language; a business person may win lucrative contracts with Japanese or Chinese businesses.
What field do you want to go into?
@Mynaaa I was thinking of a construction start up. I might want to open up a branch in Asia (If I become successful lol). So I wasn’t sure if I should do Spanish or Mandarin. Also I might get to pair either language with Arabic if possible.
If you’re thinking of eventually going international, keep in mind you could expand to Latin America if you’re good in Spanish.