how to get a hardship license

They used to be called a hardship license.... the newer term is an occupational license.  Basically, it's a limited license that authorizes your son to drive at specific times for specific purposes.
The process is relatively simple and you can sometimes find forms online.  The process starts with the petition or application for an occupational license.  It can be filed in the county where your son lives.  Some courts will let you set an hearing immediately, while others will make you wait a couple of weeks... regardless, it doesn't have the same extended wait times as other types of litigation.
He doesn't have to have an attorney for this... but it does tend to go a little more quickly and smoothly if he does have an attorney because the attorney will be able to talk to the judge, persuade them on the need, and get your son into a final hearing sooner.  The last occupational I did was filed on a Wednesday and finalized two weeks later.  So.. a relatively quick process.
Once the judge grants the request, he'll sign an order.  If your son is representing himself, he'll need to have an order ready for the judge to sign.  The main thing is to make sure that he gives him self realistic driving times and locations for his employment.  He he works in one county, but lives in another, he should request permission to drive in both counties. 
After the order is signed, he should get two certified copies of the order and take on to the local DPS office.  He should keep the second copy in the vehicle he drives at all times he drives.
As far as costs.... many online forms are free.  His main expense will be the filing fee.... which depends on your local rates.  He can also have someone draw up the paperwork and then he can walk it through himself.  This shouldn't run more than a couple of hundred dollars because it's a relatively simple motion and order.  Full representation is bit more pricy... but not that expensive:  $500-1500.... just depending on the hourly rate of the attorney and whether or not filing fees are included in their quote.  Someone may quote a low price, but then add of filing fee's afterwards.  So... when you get a quote, be sure to ask if it includes filing fees or not.