Under the laws of all states in this country as well as federal law, one cannot per se discriminate on renting to a person based upon age. There are certain exceptions. For example in a retirement community, but that is another matter. For you to refuse to rent to a person solely because he or she is under the age of 30 could subject to to a legal action by the Department of Fair Employment and Housing.You can refuse to rent to a person based on age, but you could as a result possibly end up in a lawsuit.