There are many groups and communities that have many low-cost options. Check with your Veterinarian and local shelters. Don't forget advertising costs, and sitting by the phone waiting for buyers. A neutered male has less chance of developing prostate cancer. Spaying a female dog eliminates the possibility of uterine or ovarian cancer and greatly reduces the chances of breast cancer.
Altered pets are more affectionate and loving companions.
Spaying a female dog will eliminate the mess of having her go through heat two times a year. Spaying a female cat will end the constant crying. Stud dogs and Toms will no longer visit if your female is spayed. Unaltered pets tend to exhibit behavior and temperament problems. Unaltered male cats tend to spray, run away, get into fights, and roam the neighborhood.