Ha, assuming you yield LOW amounts at 1 ounce a plant, I'd go for about 10 plants hopin for 5 to be female and there is 5 ounces which would last me about a month and a half. But if you grow right, vegging for 2 months then flowering for 2 under HPS's, I'd say you could get anywhere from 2-4 ounces dry per plant, even up to 5 or 6 depending on strain and how experienced you are.
Novice grow, try about 8 plants, hope for 4 females and you'll be lookin at around 6-8 ounces. Replant every 2 months for a constant supply.