My friends run a CSA as well as doing farmer's market and a couple of restaurants. Their CSA this year was 50 families, and that was full time work for two people, to plant, care, and harvest.
The way the CSA works, people pre-pay for a share of the crop during the season of x weeks - number of weeks and beginning or end of season is up to you. The amount they paid is divided up by how many weeks. So for example, each week you would pack up $25 worth of produce per share, if $250 was charged for a ten week CSA. So how much of each product you would have to deliver is reckoned by a market price for each product. Most popular here are tomatoes and peppers (hardest to grow here!) peas, beans, and herbs like basil, cilantro are always welcome. There is always salad greens, kale can be too much if you get it every week, so my friends have tried alternating kale, chard, bokchoy on different weeks. Broccoli, squash, cabbage, potatoes, onions, leeks, garlic are only available for a few shares during a season so nobody objects. Beets and carrots and turnips seem to be well accepted too, not usually seen every week of the year. My friends do some less common vegetables like kohlrabi and fennel too, and the CSA folks get to experience something they might not have bought in the supermarket. Ultimately you have to provide a diversity of veggies every week, as no one can eat $25 worth of lettuce or kale alone, and change it up each week as much as possible.
As Joseph commented about waste, $25 worth of veggies a week is sometimes too much for the folks who paid for it. Maybe doing more but smaller shares for a lower price would fix that. Also think "how many kinds of veggies" it takes to fill up $25 for a family. It takes a lot of planning and management, and space!.. to keep that much variety in play all season long. It would be easier to do a simpler and less expensive version, eg a 'salad CSA' where you deliver a week's worth of salad materials for say $10 a week.
Crop failures, nothing but lettuce - yep it is stressful for the farmer when a crop is not on time or failed or not enough to serve the CSA, and there's no way to deliver the share value for a given week. My friend will commonly buy any tomatoes I can spare, and even this year which was lousy and late I did sell her what she needed to cover the CSA when her tomatoes were just coming in. Outsourcing is ok but limited since local sources of organic product are not many. Sometimes they have added a share at the end of season to cover the value that was short at some point. It can be hard in a bad year. But the benefit of a CSA to the farmer, is that regardless of those shortfalls, the farmer will be able to pay herself the same amount every week of the season, and not have to go hungry in the week that there's 'nothing but lettuce'. If you don't need that kind of community support, no reason to do CSA, for all the reasons that simply going to market with your surplus when you have some is an easier gig.
