What are the questions to ask when hiring a long term project engineer

I was told I would be better off to hire a committed site engineer to build my site. The reasons for this is that it not an easy site to build and it is the business.It will forever be changing , adapting, and growing as our audience needs dictate and opportunities develop.So my question is what is the criteria I should use in bringing someone on board and who has the flexibility and foresight to adapt the site to changes in technology and customer needs.This person should have a vested interest in the site too. Live or die.Thanks