The Internet has opened up opportunities unheard of 15 years ago.
In 2002, in Prague, I met a man who identified himself as a collector of first editions. I asked him how to learn the values of such books, as I had a couple in my collection, and he told me abebooks. I went back to my apartment and learned that my copy of the Acrobats, Mordecai Richler's first novel, printed in 2000 copies, was going for about $200. I was hooked, and began scouring the Prague shops for English books. I was fairly successful there, as the Czechs didn't know English, and most of the English books were from the period between the world wars. I picked up remarkable books for a dollar or two. Upon returning to Israel, I found prices a little bit higher, but in general I could still build up my collection. It took me until 2007 to have enough books to post them online, and begin paying a monthly fee. Because I concentrate on rare books with a high mark-up, I have always made more than the annual fee, even if only a dozen books were sold over a calendar year. Over the years I have become something of an expert in my field, and was recently offered a job pricing books for a big book warehouse. What began as a hobby with benefits is turning into an occupation.
Without the Internet, I never would have found a market for my books.