~$1000 a month. Designed, edited and published a book of Warren Buffett's letters to shareholders (see http://amzn.com/1595910778). An opportunity I stumbled into. But I suppose "get publication rights from Warren Buffett" isn't a repeatable business model :)
Not repeatable in that specific case, but have you thought about doing the same thing for other high-profile figures (either in finance or elsewhere)? You might be able to leverage your experience and success to get them to agree to a similar sort of thing...
I have thought of this but haven't really pursued anything yet. I also have permission from Buffett to publish his early partnership/hedge fund letters from the '60s, so will probably be doing that in the next year.
Interesting! I saw the book a few weeks ago and wondered who put it together. I assume the letters are public? How did you get the extra material? And do you share any income with Buffet? (That would feel strange, but would also make sense)
Most of the letters are freely available on Berkshire's website. The "extra material" includes a few early letters not on the web (got these from Buffett so the collection would be complete), and charts/tables/indexes that I put together myself.
The income is not shared with Buffett, but any income I receive is "return on capital" from me taking inventory risk. So I do have to invest some of my $$$ to buy the book inventory, and as it's sold to Amazon I make (great) return on that money. But the profit per book is actually pretty low compared to other published books -- I could be charging much more for the book, but it was part of our "agreement" that I make the total price of the book as cheap as possible. (Which I think is accomplished with Amazon's price of $19-25 for a 700 page textbook-size book.)
