When you dip into a nonfiction book, hunting for a particular piece of information, your first stop is the index at the back. There's everything neatly organized, alphabetically by subject matter with the exact page or pages on which to find that nugget of data. Who puts together that index, tidily chronicling each page of text? If you love books and snippets of fact, you're detail-oriented and a stickler for accuracy, it could be you as owner of a book indexing service. The advantages to this business are that you can start on the proverbial shoestring, your overhead is minimal, and you get to learn all sorts of interesting things from books on a wide variety of topics. As a book indexer, you'll need to have a highly organized, detail-oriented personality--this is a business where nitpicking is a virtue. You should enjoy books and the written word and be able to put in long hours hunched over a manuscript without suffering the fidgets.
Your clients will be editors and publishers of nonfiction books. You can live anywhere and work with clients in New York, California or wherever they happen to be based. The best way to solicit business is to call editors and offer your services, then follow up with a letter and your business card.
All you need to get started are a computer with a laser or inkjet printer, the usual office software, and a comfortable work space with good lighting.