Hiya, are you talking about google adwords? if so then they can either make you plenty, or cost you plenty. My advice to anyone who is considering using adwords, is to sit down ad spend a lot of time learning how they work.
Learn about the different types of matching, broad, phrase & exact etc. Learn about how ads are shown geographically. Learn how to control your budget. and learn to turn off the option to show ads via content matching. You can look at that later.