As someone who sells a lot of info products, I’d like to share with you how I do my audio interviews. I use a piece of equipment I picked up at B & H Photo. It’s called a Marantz PMD 660. I use either that or another similar product, the PMD 670. Both record onto a flash memory card.
The microphones I use are some fairly standard Shure corded mics. As long as you have decent mics (ones which cost over $50, you should be OK) and good mic stands you’ll be good to go.
The most important part of this process is HOW you do the interview. Take a look at a seminar I’ll be doing!