Where do historians get the information on life of Nazareth?

Answer 1

Archaeological finds in Nazareth that might date from before Christ have been found including irrigation systems and other agricultural structures, winepresses, watchtowers, pottery, and quarries.

Answer 2

Historians have not been able to establish with certainty whether Nazareth existed before 70 CE and the end of the First Jewish War. There is archaeological evidence of a village of Nazareth late in the first century, and historians accept that life in Nazareth would have been much like life in any other Jewish village in Galilee. They also know about Galilean life in the second part of the first century, from the works of the Jewish historian Josephus.

Wikipedia describes the state of Archaeology in Nazareth, indicating that no worthwhile evidence of a settlement has yet been found from the time of Herod or the start of the first century CE. We must wait for further evidence.