Coin collecting can be both personally and financially rewarding. If you are considering turning your numismatic hobby into a business, you may be farther along that path than you are aware. The contacts you've made as a collector are readily transferrable to your new dealer status.
Start the business. If you are already well-vested in the hobby, beginning a business as a dealer may be as simple as hanging up a shingle over your own collection. However, if you're looking to turn your hobby to a long-term, profitable business, you need to be willing to invest time and money in the foundation. Start with a company name, business cards, and a website.
Create a library. If your bookshelves are not already lined with books on coins, becoming a dealer may be an unrealistic business model for you. Books such as The Official Redbook: A Guide Book of United States Coins; The Official American Numismatic Association Grading Standards of United States Coins, and the latest edition of U.S. Coin Digest are probably already staples of your coin library. However, you should also subscribe to magazines. Krause Publications publishes Coin World, Coins Magazine and Numismatic News, all of which are worth taking a look at.
Research coins and coin collecting. Before you can sell coins, you need to understand what will sell. Understanding coin value means knowing what is rare and what is in demand. While all numismatists want to get their hands on error coins or a 1969-S Lincoln penny, setting realistic sights is important.
Learn how to grade coins properly. Grading is about the condition of the coins and, if you do not understand the full worth of the coins with which you will be dealing, you will never be a coin dealer. The grading book in Step 2 is certainly a start, but nothing can replace hands-on training. Practice grading coins new to your collection against coins for which you already know the grade.
Build your collection. Purchase from coin and antique auctions and from fellow coin dealers. Once you have a good handle on what the buying public wants, buy what you can afford. Buy what sells.
Self-promote. Place advertisements in coin magazines and online (in places like eBay and Craig's List) to gather inventory and clients. Attend coin shows, join online coin blogs, and put yourself and your company out in front of the public. Consult the American Numismatic Association for upcoming events and information on coins and publications.
Offer personal service. Take orders for specific coins when you can, and use your connections to satisfy your clients' wants.
Be honest. If you want success in an industry that sometimes includes unsavory participants, being honest about your product will guarantee you repeat customers. Being a coin dealer means cultivating relationships with your vendors and your clients.