So it seems like you are asking how many raised bed
per CSA and then you will just multiply that by the amount of CSA boxes.
So I need a few clarification:
1) Is this a weekly CSA, if not is it bi-weekly, or monthly.
2) Is this vegetable only or vegetable and herbs or something else.
3) How long is the CSA for, just summer (13 weeks) or is it 26 weeks (May-Oct), or something else.
4) How much are you effectively getting paid per week. ($520/26wks = $20/wks)
5) How much do you effectively charge pound. $4/lbs and $20/week = 5lbs/week.
6) How much produce do you provide per week. $4/lbs and $20/week = 5lbs/week.
Time to Maturity = 7wks,
Harvest per week = 5lbs,
Space required per lbs of harvest = 2sqft
Space required per week = 2 * 5 = 10sqft/wk
Total Space Required = 7wks * 10sqft/wk = 70sqft
Each week you harvest a batch, just replant some new ones.
Add some fertility after each batch, maybe
After each weekly harvest change species/plant family, to help with pest control.
What are the list of vegetables that you will be providing?
Spinach Family (Rainbow Swiss Chard, Beet Tops, etc)
Cabbage Family (Kale, Collard, Cabbage, etc)
Lettuce Family (lettuce, maybe dandelion greens)
Herbs (Basil, Thyme, Oregano, Winter Savory, Mint, Chives/Scallion, Celery/etc)