The short answer is yes, you can buy a mailing list for almost every demographic you can think of, and the list will be pretty good and not too expensive. Whether it is a good marketing idea depends on too many factors to answer here. Why don't you contact a local small
PR or Ad firm that can guide you without costing an arm and a leg. A local college's business department might have student run clinics or professors' private businesses that are cost effective. Believe me, paying a professional marketer a few bucks will make your advertisement infinitely more cost effective.