I am currently working on multilingual application for smartphones as well as webiste supporting this app. If you have descent developers they shouldn't have problems developing multilingual application/website at all. When asked that question myself, my developers told me, that everything you have to do in order to add new language, is to make list of all text lines in one document and then simply add translations (assuming code is descently written).
Last thing I would request from developer is speaking multiple languages. It's tough enough to find descent developer, who is good at writing code and you don't want him to think about anything else but programming.
I think you should outsource translations somehow, either try checking through your international connections or find translators on freelancer websites. I don't know how wide your web is, but after all there usualy isn't that much text to be translated, so hiring a full time translator is usualy a bad option.
However if you are going to look for freelance translators, try to agree on keeping their contact information as you might need them for future minor tasks.