From the questions you are asking it doesn't sound like you know too much about Marijuana Cultivation. I would highly recommend you start lookin' around for Cannabis growing guides because your first time with that many plants, you're bound to mess something up. A few years ago books and guides weren't as easy to get if you didn't know what you were looking for but now you could probably do an easy search on Google for some guides. I would not recommend going straight into this planting as many seeds as you plan without any experience. Maybe you have more confidence but I wouldn't risk wasting all the possible bud you could get if you had done it right. If your friend grows weed maybe you could learn from him or maybe he could help you maintain your garden.