Breeding is never an easy way to make money. Done right, breeding is rarely a money-making venture. If there are any problems at all , breeding can become a financial disaster. So, you have to be prepared for possible expenses that may or may not occur. Keep a credit card cleared off, a credit on your vet account or a yorkie bank account in case it's needed are a few good ways to prevent lack of whelping care at the vet's.
Most breeders get a deposit of some sort from potential buyers at some point, whether on a waiting list or after the pups are born. However way you do it please be sure to carefully explain under what circumstances you will or won't return the deposit so as to avoid unpleasantness in the future.
Whatever your deposit arrangements, you should demand payment-in-full before turning your puppies over to the new owners. The price of the puppies depends on the market in your area. Ask around among other breeders, consider your expenses, and set a fair price for your puppies.
If you have a large litter with no problems, you can expect to pay your expenses and, perhaps, make a little extra money. If you have any problems at all, including a small litter, you will probably loose money on breeding a litter. Done correctly, breeding puppies is no way to make a fortune.
Information gathered off the WWW, books, experience and advice.