Check with your local animal-control authority to see whether you need to obtain an exotic pet permit when you legally own a marmoset. While ownership of marmosets is usually allowed in most jurisdictions, an inspection from an animal-control officer may be required to determine that you have created a satisfactory habitat for the animal.
Contact the Animal and Plant Health Inspection Service (APHIS) of the USDA if you plan to breed, exhibit or sell a marmoset. An APHIS representative will schedule an inspection of the animal and request all veterinary records before a license to sell, breed or show your pet marmoset will be granted.
Find a veterinarian who will treat your exotic pet before you try to own one legally. Your neighborhood vet should be happy to refer you to a primate specialist in your area if he is not prepared or willing to treat the animal. Your pet marmoset will need appropriate vaccinations and checkups on an annual basis, and all medical records should be kept handy in case of an APHIS inspection of the animal.
Ensure that a pet marmoset breeder has the appropriate USDA license, with documented APHIS inspections, before you purchase an animal. Some primate breeders are unscrupulous and may try to sell you an unlicensed marmoset for some quick cash. If a breeder cannot provide appropriate documentation to accompany the sale of a marmoset, you should report her to the USDA.
Prepare and maintain the proper habitat when you legally own a pet marmoset. These primates can be quite destructive if unsupervised, so a large and sturdy cage, preferably with a volume of more than 200 cubic feet, should be built. Marmosets can subsist on a rotating diet of fresh fruits and vegetables, as well as whole grains, such as pasta and cereal.