This is an excellent question and one I often hear for any type of product or service in need of attention. I've successfully built both profit and non-profit businesses using grassroots methodology. Here is what I suggest as a great low-budget starting point.
Your project is very similar to the book "Think and Grow Rich." Your audience will be best built using your interviewee as the anchor. Anchor meaning, the reason people are tuning in to listen or download your podcast. If you can interview someone everyone knows like Mark Cuban or Damon John, I'm sure you'll be widely successful from show #1. However, if they are unavailable look for others people to interview who have a footprint larger than yours. Who is the most famous entrepreneur you know? Now, who is the most famous entrepreneur your 5 closest friends know? You see what I'm getting at? Find someone who brings an audience with them.
If the person you interview tells their followers and fans, and you tell your followers and fans, your initial show will be awesome. As you build more great interviews, people will begin to tune into your podcast just to see who else you might have on it. Be sure to send an invitation to the local business newspaper and to bloggers who might listen in and then write about your show.
Be sure to post new podcasts often and make wise interview choices with great interview questions. You may also want to ask the general public the questions they want you to ask.
Build your podcast in this grassroots method and you'll have all the audience members you need progressively. Good luck. Contact me at any time with any follow-up questions.