As many others have noted, charging for a podcast is a very difficult task Pamela, especially if you do not have a name in the field.
I subscribe to a lot of podcasts and do not pay for any of them. I listen to them when they seem appropriate. I have never paid for a podcast and don't plan on ever doing so, though I have bought audio downloads at times. That might be a better approach.
Though this could just be a matter of terminology. A podcast implies a regular "publishing" schedule of some sort. Are you talking about an ongoing series or just a one-time thing? What would draw people to your podcast? What expertise do you have in that area that would compel people to want to hear you?