What are the starting costs?

One of the appealing things about being a writer is the low starting cost. If you are good at writing and can find a subject where you can add value, and an audience that will appreciate it enough to pay you for it, you are ready to go. The last part, by the way, is the most difficult.
It used to be that things were the other way around: The audience had to find the author. They could do so very easily, since there were a limited number of outlets, the outlets had a limited number of authors, and the outlets advertised their location clearly.
When books ceased to have physical form, that business model went out the window. The audience is finding new meeting places, and even though the physical distribution of books is still a major business, the electronic distribution is gradually forcing the actors out of business. If you have to pay for the reading apparatus every time you buy a book it stops being economical when anyone with a PC can read the book and only has to buy one PC once. Or tablet, or smartphone.
The production side is also much cheaper. In the 19th century, books were composed manually, each letter laboriously placed into the frame by a highly specialized craftsman. As industry advanced, typesetting by machine became possible. But the books still had to be printed. And printing changed once in fiour hundred years, as the flatbed press was replaced by rollers. The next change did not happen until composition went computerized. And now the ebook is replacing the paper book, the trees finally about to be left standing accumulating carbon dioxide instead of being cut down and turned into paper for books which will be read once. And then turned to toilet paper and be flushed. 

But that was before Amazon arrived with the Kindle. So you can now publish a book without investing anything in printing or distribution. Sure, Amazon takes 30 % of the money, but old-style bookstores took 50% and that was for books that you had to have printed. 

The only thing you have to do as an author is write the book, edit it a bit, format it a little and then publish it literally by the punch of a button. You are supposed to submit it in the special ebook format Amazon uses, but they also accept .doc files. You do not need to pay for Microsoft Word to produce a .doc file either, you can use the free OpenOffice software. All you need is a computer and Internet connection. Yes, you need a browser too. Use Firefox, it is free and much better than others. Especially Microsoft Explorer, if you use Windows. 

In a pinch, you could write in Google Docs and save your stuff on Google Drive, so you do not even have to have a computer. If your public library, or the shelter where you stay winter nights, or your grandfather or anybody has a computer you can use, you can write and publish a book. You can turn work into money. Without having any money first. Literally.