Yes, Atticus does "help out" Walter Cunningham, but Cunningham is not the type of man who will accept charity.
Whenever one reads a novel, it is important to continuously consider the characters within the setting that the author has created. With the setting of the 1930s in Harper Lee's novel, there are two major factors: the Great Depression and the Jim Crow South.
Mr. Walter Cunningham comes to Atticus Finch for his legal affairs--his "entailments"--and because he, like so many others, has no cash money, he pays Mr. Finch with produce from his farm, such as a bag of potatoes, etc.
As the Cunninghams had no money to pay a lawyer, they simply paid us with what they had. (Ch. 2)
Mr. Cunningham is too self-motivated and proud to become a dependent of the government and work for the WPA, the Works Progress Administration, a program that paid unemployed people to carry out public works projects (e.g. the Hoover Dam, the Tennessee Valley Authority, etc.) instituted by then President Franklin D. Roosevelt.
Although poor, Mr. Cunningham stands in sharp contrast to the shiftless Bob Ewell, who willingly submits himself and his family to being dependent upon government relief checks, even wasting the money on drink and neglecting his children.
I am uncertain as to whether this question is referring to Walter Cunningham Sr. or Walter Cunningham Jr. It doesn't really matter because Atticus helps out both of them. The previous post mentions that Atticus helps Cunningham Sr. with some legal "entailments." Atticus takes Cunningham Sr. on as a client knowing full well that the Cunningham family is too poor to pay with money; however, that doesn't stop Atticus from offering his services. He knows full well that the Cunningham family will pay him in one form or another.
That spring when we found a crokersack full of turnip greens, Atticus said Mr. Cunningham had more than paid him.
“Why does he pay you like that?” I asked.
“Because that’s the only way he can pay me. He has no money.”
Atticus helps out Cunningham Sr. by being willing to take him on as a client in the first place. Other lawyers would probably have turned him down. The fact that Atticus is okay with receiving material goods for payment is also a big help to Mr. Cunningham because it allows him a way to pay for the services he's getting from Atticus. This is important for the Cunningham family because while they are poor, they are not okay with taking handouts. This makes the Cunninghams stand out when compared to the Ewells.
Atticus also helps out Walter Cunningham Jr. In chapter 3, there's a great little scene when Walter eats a meal at the Finch household. Atticus graciously welcomes Walter into the house and talks to Walter as if Walter is a well-educated adult farmer.
While Walter piled food on his plate, he and Atticus talked together like two men, to the wonderment of Jem and me.
In a nutshell, Atticus doesn't treat any of the Cunninghams like they are inferior members of Maycomb. They might be poor, but that doesn't make them inferior people. This is distinctly different than most people in Maycomb. Atticus's greatest help to the Cunninghams is by treating them like equals.