Who should pay for fixes/bugs? [closed]

Question

So I just started freelancing both in desktop/web development and this client who already accepted my work, and payed me keeps coming back at me each time he finds a bug etc. And I have found myself spending more time than I thought fixing them for free. Is this alright, or should I start charging a support fee?

Which is the best way to deal with fixes on a supposedly accepted and completed work?