You want to try and bring a character to life in an honest a way as you possibly can. It doesn't matter whether he's a doctor an actor a car salesman or a captain of a starship. If you can bring truth and honesty to that character then your audience will believe you.
You hear entertainers all the time saying 'If I couldn't get paid for this I'd do it for free.' When's the last time you ever heard a business person say 'If I couldn't get paid for being chairman of British Petroleum I'd do it for free'?
