You're entering a new niche with zero experience and credibility, and you need an incentive to offer visitors to get them to join your list. What do you do?
You could of course buy PLR, but you want something unique to you. You could spend a couple of weeks researching and writing your own unique report, but again – you have no authority in this new niche, so that report of yours isn't going to carry a lot of weight.
But what if you could leverage the experience of 20 or 30 experts into creating your report? And better still, what if you could actually use their names to market your report?
This is the idea behind interviewing experts in your niche and compiling the transcripts of those interviews into one valuable book. Simply make a list of people you'd like to interview and send each of them a personalized email. Tell them in the subject line that you want to interview them, and in the body of your copy tell them the theme of your book, what you hope they can contribute and most of all, what's in it for them.
This makes your list building incentive easy to make, since most of the content is contributed by experts. You get instant credibility for being associated with these experts. And if you choose a good them for your book, you might even enjoy a viral effect as people tell other people about your free incentive.