How do I aquire a certificate/permit to breed mice?

You can apply to the USDA for a license, but quite frankly, their license means very little. With hamsters, one of the requirements is that each hamster has at least 3"X5"-that is the size of a notecard. They generously require that a female with babies have at least 4"X6". Their standards consider cleanliness, but not the treatment of the animals. You would be better off to be a responsible breeder who networks with other breeders to share information and quality breeding stock, then selling to local stores that are interested in buying quality animals locally. Most of the large chain stores are only interested in bulk quantities from large distributors (they claim it is due to licensing, but we all know that is not the case). Providing a local resource for small animals is a much safer, less stressful means of providing pets. It's nice to know there are people out there who want to be responsible breeders and do what is best for the animals.