Audible Originals

Audible is a publisher like any other, these days. They'll pay you an advance, they'll provide an editor and a narrator, they'll promote your book. They only want the audio rights, although they may ask for an exclusive for some months before you can publish the text versions. I've gone this route, and my text versions are essentially self-pub--my agent take care of the mechanics so I guess he's my publisher, but it's only Amazon and POD paperbacks.

The thing is--and this is the kicker--audio is a largely untapped and quickly expanding market. If you look at Audible, or for that matter any big-5 publisher's audio wing, you'll see not all that much product, compared to the 5 million plus titles on Amazon. That's because there's an up-front cost if you want to self-pub audio, probably somewhere in the neighborhood of $2K.

Audible has been 2/3 to 3/4 of my revenue from my books since day one. And that despite a slightly smaller per-unit royalty.