As has been said, without knowing the subject it's difficult to give specific advice.
There are many groups and organizations out there that have their own specific interests - the Civil War, show dogs, Shakespeare, fly fishing, family ancestry, politics, ice carving, you name it. Contact several groups and just tell the head honcho what you're doing and why. Make sure that you have your pitch ready and your project outline completed as well as having all the paperwork ready before you ask (release forms, etc.).
As far as pay is concerned most people are willing to do it for free. Treat them with courtesy and respect. And for damn sure make sure that you and your crew are on time and fully prepared in terms of both process (questions, etc.) and technically (everything works and you all know how to use it) so you do not waste the time of your interviewees. It also insures more cooperation and a more comfortable interview if you and your crew come off as thorough professionals.