Refusing to rent an apartment to someone based on the number of children they have is discrimination, and is illegal in most states. However, given the amount of damage a pet can do to an apartment, even a well kept pet, and given the fact that a pet is a pet and not a person (sorry, lady) I can understand a landlord not renting to someone with pets, or charging extra. A law requiring landlords to rent to people with companion animals is a major violation of private property rights, especially if it leaves the property owner no legal recourse to take if the apartment is damaged by the pets. Even a small pet like a cat can do major damage to an apartment, and the scent from a litterbox can linger for a long time, making it difficult for the landlord to rent the apt again without a serious cleaning bill.