Is my basement apartment automatically illegal?

A basement apartment is not automatically illegal just because it exists, but renting it out or counting it as legal living space generally requires meeting building code items like proper egress, ceiling height and separated utilities, plus the permits that go with them. Many basement units around North Metro Atlanta operate without those permits, which creates risk for both owner and tenant if something goes wrong. Checking with the local building department is the only way to confirm the status of a specific unit.