Greenhouse

I just purchased a 70'x 30'greenhouse. First greenhouse I have ever owned. It is on property that I want to lease. I have worked in a green house before and have had a successfull garden for the last 10 years. I want to start to grow and sell basil and other herbs. I have a few local restaurants that are interested. The demand I would like to start with is around 20lbs of basil a wk. harvest. How many plants do you suggest I start out with to reach my goal. And how much space would this take.
Thank you for any suggestion you may have. I know this will take time and energy that I am willing to do.

Thank You