Free legal aid is a program aim to assist low income people in resolving any issues they have with say the Welfare office, social security (denial of benefits, reduction of benefits etc.etc.)...and other public institutions. Each program have its own set of rules...also it depends on which city, county and state you live. Check it with your local legal aid office, they are in the white pages under government...usually under county.
There are special DUI lawyers - but they actually cost more.
For a DUI you probably already realize there will be a criminal case against you in a court as well as a separate administrative case against you by the DMV.
People tell me the attorney starts out at $3-4,000. Included in the price is requesting a copy of the police report, patrol car camera if there is one, and recordings of what the police officer said to dispatch over the police radio. The lawyer will also go to the DA and ask for a deal.
You can do all of the above by yourself. They charge you a fee to make copies of the report and video and audio. Budget about $200. Then you can go to the DA and see what their standard deal is. If it is your first offense, and you were cooperative with the police and you didn't cause a crash - in my area they let you plea to DWAi which is less severe than full blown DUI.
Where a lawyer earns his money is if he finds some discrepancies in the whole arrest proceeding. There is pretty much no way you would be able to do this on your own.
Next your attorney may charge you and extra $2000 to represent you at the DMV administrative hearing. However, you are pretty much guaranteed to lose this one.
Finally, if you take it to jury trial your attorney may charge you an extra $4-5000.
Imagine, if you found an attorney who didn't know anything about DUI to take your case for 1/2 price? What would this accomplish? Nothing you could do that much by yourself. It's actually pretty rare for a DUI case to go all the way to trial - 99% of the people just take the deal.