You have to find something else to do, because it is hard to find work if you haven't by the time you take the bar. And there's no guarantee that you'll find something immediately, even after that.
And even with the DA's office, you need to try and get some experience there, if you don't already have some in criminal law. Since you do have to survive, try to find a good part time job--law clerk or paralegal that actually pays enough to try and live off of for a few months, very frugally-- and spend the rest of the time at the DA's office. If that is really what you want to do find a local office and intern there, so as soon as you pass the bar you can be ready for any openings that might be available.
So many people think that this work is easy to get for some reason. With the DA's office, any government positions, public interest, they want to know why you want to work there, and they want to see some sort of past action that reflects that. If you can't, they can easily find someone who does.