not much.. it would be immature.. that means a smaller yield and less potent smoke... if you let it veg to maturity you will get the most out of it both yield wise and smoke wise.. but 12/12 straight from seed you'll get something.. just dont look for anything to write home about..
One month is not enough time for the buds to mature. You would only get a few grams of immature bud - not even worth the time.
12 / 12 from seed is one thing, but even at that you will need a couple of months.