Okay, this isn't to say that this is easy or there aren't cons. There are. Lots of them. Which is why, I imagine, there's not a lot of Kindle talk around this forum.
Con #1: It's a LOT of work. Even if you're outsourcing. I started by doing it all myself: research, writing, formatting, cover design, uploading, marketing. Everything. It's a huge time investment, and I suspect this is the step that scares most people off.
Con #2: It's NOT instantaneous. We're always looking for quick money in the IM world. Kindle is not that. It takes time and effort to build up an audience, to learn how to outsource correctly, to streamline the process for efficiency. It's worth it, but it does take a great deal of time.
Con #3: Kindle is not PLR friendly, is not article spinning friendly, is not black hat friendly, etc, etc. This probably also scares a lot of people off. Mess with Kindle, and it will blacklist you. But even playing by the rules has gotten me much more than black hat stuff ever did.
Okay, it's not all doom and gloom. Let's see some pros.
Pro #1: Once you've uploaded a book, it's (nearly) set, forget, and earn. My very first book took me a long time to research, write, format, etc. It was a pain. But you know what? Since I uploaded it 2 months ago, I have done zero marketing, zero promotion, and have spent zero effort on it. Guess what: it's still averaging about 10 sales per day. That's with zero work on my part. IMO, that's well worth the initial effort. A few days pain for recurring money daily - I'll take that any day.
Pro #2: Tied in with Pro #1 is the fact that, if you sign up for KDP Select, you hardly have to do any marketing (unless you want, of course). I have a series of books in a non-fiction, educational sort of niche. I have done zero marketing on them. No blogs, no twitter, no fb, nada. All 4 books are in the Top 10 in their Kindle category. If you create a quality book, Amazon will market it for you. It will start showing up in people's feeds, in "people who bought X, also bought Y", and all that type of stuff. It's beautiful. Set and forget.
Pro #3: Once you get a system down, you can easily produce a book a day. Even if you only make one sale a day, that's $2. You have 10 books? That's $20 a day. You have 50 book? Hello, $100 per day. The possibilities are endless. Literally.
Okay, okay, enough of the rant. Just wanted to share what (I think) is an under-looked market on this forum. Yes, it's not black hat. Yes, it's not quick and easy money. But it's sustainable and, if done right, really profitable.
Do your research (I'll post more on this later, if wanted)
Produce (or outsource) quality content.
Enroll in KDP.
Set a goal of 1 book per month, per week, or per day even (if the quality doesn't suffer).
Use the same pen name for similar books, to build up an audience and make each book easier to find.
Put links to your books at the end of all of your other books, to make them easier to find.
Sit back and enjoy.
Rinse, Lather, Repeat