Do I need two tents, one for veg and one for flowering?

With one tent, the plants flower where they grew, and you simply wait between harvests. A second, smaller tent lets you keep mother plants or the next round of plants on 18 hours while the main tent flowers on 12. That gives you a more even rhythm, and it's handy for cuttings.

It is not a beginner requirement. If you do want the extra space later, a small tent for cuttings and seedlings next to your main tent does the job.