I use to raise Yorkshire Terriers. Monetarily speaking, they are one that pull a nice price. But counting time and money invested, no it's not a good means for stable income. I had four girls in home and two studs. I bred for quality akc standard companions, not for show. The economy has really affected new homes looking for puppies, especially during the summer.
In every breed there are backyard breeders who treat the dogs poorly, have way to many, and don't care about standards. The byb tactic is mass selling for cheaper. I found many times, the potential puppy owners want a cute puppy at a cheaper price, and full registration so they can get their money back by breeding. They probably do make money, but are hurting the pet population severely. And breaking hearts of pet owners who end up with a sick dog. In all, it's a wonderful experience if done right, but little money considering possiblec-sections, vet care, supplies.