Congratulations of finally getting the chance to play banjo. Your eagerness is great motivational fuel, and it's important you use that "fuel" wisely.
In my opinion, it's not necessary to get a teacher when you start out. There are good books and DVDs to help the beginner get started. First you need to learn to tune the thing (electronic tuners, for as little as $20 or 30 make it easy. I recommend a good little clip-on one sold under the name Intelli or Meisel.)
Then you learn a few chords and get comfortable changing chords smoothly. Once you can do that, you're playing! Use any strum at all for the right hand (OK to just brush the strings with a finger or thumb) and follow the chords to a song. Next you learn a 4-note roll pattern, then later, 8-note roll patterns and change out the strum for rolls, still changing chords at the right time.
This process is outlined on my "ultra-easy" DVD Get Rolling, which is only $20. Once you feel ready to tackle Scruggs style, there's a full beginner's course (Beginning Bluegrass Banjo), as well as some play-along Bluegrass Jamming DVDs that would be quite helpful. In terms of economics, these items can show a banjo player a tremendous amount of material at low costs ($30 each DVD).
A teacher is often not necessary, though one can be very useful if the student needs guidance in using the videos. If you find you would like some guidance, a non-threatening but musically knowledgeable person who appreciates bluegrass would be the best choice. You could try a guitar teacher, for example, and show what you're working on and ask, "Is this right?"
For more information and ordering the DVDs, go to the Store section of DrBanjo.com. Also, the beginning banjo player can find a lot of free material on my site, including an article summarizing my recommendations for learning, "Teaching Beginning Banjo Players". It's in a section of the site under Instructional called Beginning Banjo Player Resources. I can't recommend strongly enough that you read this article. My ideas about learning bluegrass banjo are different from most teachers', and I think you might save a lot of time getting more directly to real playing if you follow my advice.
I hope the above is of some help. Have a great time with your new banjo!