Atticus is close to fifty. We learn this when Scout states:
Atticus was feeble: he was nearly fifty.
This is meant to be a comic utterance, saying more about the young Scout's perception of age than anything about Atticus. Most adults would not consider people in their late 40s "feeble," and we are meant to smile at Scout's innocence.
Scout contrasts Atticus to the younger parents of her school peers. Atticus doesn't like to play football with Jem, and unlike her friends' parents, Atticus doesn't fish, play cards, drink, or smoke. He simply sits at home and reads. He also doesn't have jobs like her friends' parents: he doesn't work in a drugstore, drive a dump truck, and is not a sheriff. In her words, he does not do
anything that could possibly arouse the admiration of anyone.
Of course, Lee writes all this tongue-in-cheek. Being a lawyer is a higher-status job that any that Scout lists. And as the chapter goes on, Atticus will reveal he is a sharp shooter and a courageous one at that, killing a rabid dog and earning Scout's boundless admiration.