Check with local animal shelters or veterinarian's offices to ask about pets available without an adoption fee. Also, check online classified advertising sites such as Craigslist.org. Animal shelters and humane societies sometimes offer no-cost adoptions for pets who are more difficult to place.
The issue of no-cost pet adoptions is controversial in the animal welfare community, but shelters often sometimes resort to eliminating adoption fees for harder-to-place animals, such as adult cats or large mixed breed dogs.
In lieu of a shelter adoption, check local and online classified advertising sites. Craigslist.org has pet listing in the Community section. Many local newspapers offer online classified advertising. Search Facebook and other social media sites for community pages that list garage sales and community notices, as they often feature free pet listings. Consider placing a "pet wanted" ad on these sites.
Unless a pet is acquired through a reputable source such as a shelter or a veterinary clinic, be sure to ask for the pet's background and medical history. Ask if the pet has received the necessary vaccinations, and if there is a history of aggression or destructive tendencies. People sometimes place pets in new homes for reasons unrelated to the pet's health or behavior, but go into a pet adoption with as much information as possible.