How much and how do I get rid of roaches?

I have been seeing roaches and I guess tiny babies in my kitchen. I knew they were here within my first month. But the last two weeks its become I guess an infestation. How much does it cost to take care of? Can I treat just my apt, or does the entire apt building need to be treated? What am I doing to cause them to grow? I am very clean, but my apt is only 280sq ft, so am I being unaware of some carelessness, or was it just bound to happen eventually?