There are a number of things can try yourself. Borax is a good insecticide for ants. You can leave Borax around where they seem to be coming through and see if has effect.
If you're looking for an even cheaper, less toxic solution for ants, you can find it in your local produce aisle.
And while of course there's little harm or foul with taking a natural approach, if you do opt for a pro, you can be confident that they'll use the exact right amountt of product needed to eliminate the bugs. Many people avoid exterminators out of fear of the broad-spectrum DDT that was used in years past; however, today's pesticides have evolved by leaps and bounds.
In my experience, exterminator’s are allowed to have more potent chemicals and of course more effective delivery systems. I have fixed ant and even termite problems myself but it really only works if you catch it early and the problem isn’t too bad yet. With ants, main thing is to eliminate the food source and buy an ant killer. You will definitely want to figure out what kind of ants they are, since some kinds have different pesticides . I just called a local exterminator and chatted with the hardware store guy to see what they recommended.