How do dog breeders protect themselves against bad buyers ? and still prove ourselves.?

I have always taken precautions for health and safety of my puppies,cleaning,first shots and bleaching the floors after company and shoe spray before entering (while this may seem extreme to some i have never had a sick puppy) allowing perspective new family's to my home to see the babies and being honest and clear about my dogs.I have done allot to prove myself,I don't over charge.I don't live off my dogs.I am not rich and live quite modestly. Now I have been robbed in only a short trip to the store,a buyer at fault and yes im sure .my only option is to require 2 business references before having anyone to my home,though most people don't like this.can you suggest any options? please do not respond with stop breeding, I limit breeding and produce a well bred healthy puppy its not for extra money, I love my breed and also suggest checking your local shelter I have a couple rescues myself and have reformed others so homes would adopt them.