P.S. If this relates to your own garden, don't count your chickens before they hatch. A lot can happen between now and mid-Oct. Like herbivore predation, cops, bugs, rippers, drought, storms, stuff like that.
Yea that's fine if you have the head room and a good Exhausted and intake system. As far as your question about how much they will yield you need to know the strain to have a idea about that. If you know the strain we can help if you don't then you can tell us later down the road.
A 1,000 watt HPS provides optimum light for 20 sq/ft. (example: 4' x 5')
That's enough room for 10 plants if you keep 'em short and don't top.
The 80 lbs. figure I mentioned was for a new type of growing outside that uses a plot of Fox Farms soil 10' across by 4' deep and started on 01/01 and put outside in May when 4' tall.
A friend got 5 lbs. per plant last year but I've heard people claim they get as much as 8 lbs. per plant.
8 lbs. x 10 plants = 80 lbs.
My recommendation is to construct a chamber 4' x 5' and paint the walls flat white and put in intake and exhaust ventilation.
Stick 20 unsexed plants in there in 3 gal. containers under a 24/0 light cycle. When they are 15" tall flip the timer to 12/12. As soon as they express sex ditch the males which will leave you with 10 girls (approx).
This is a guesstimate but figure 1.5 oz. per plant, or almost a pound.
How much does the fox farm cost your friend? Around here it is 16-20 dollars a bag...so that is atleast $650...but 50 pounds would be well worth it ... I used to get 2 pounds a plant but moved to the city, so there will be no more of that