Daylilies are a wonderful hobby plant, but the word on the street is that nobody gets rich selling daylilies. I do my best to help pay the (daylily) bills by selling on a few venues (including here, Craig's List and the Lily Auction). Whatever I make is nice but it's certainly a drop in the bucket compared to my expenses for materials, water, fertilizer, new plants, etc.
My question is what plan do you have to sell these and do you know what your market will be? Will you pot them and take them to a Farmer's Market (probably more of a comittment of time than you want to make)?, Can you sell them potted or bare root to local nurseries? Can you get enough people walking in to the farm to sell direct, and would that be as they showed up or would you have a few open garden days (where you might need helpers if there is a crowd) ... would you dig to order or have some in pots ready to go?
To answer another one of your questions, you can divide the plants when they are even at two fans, but it's not recommended. It's said daylilies like company so even two single fans in one hole seems to make them grow better than one fan on its own. Therefore, I would wait until at least 4 fans before dividing them into new plants.
Go to the AHS website and explore whatever information you can find there. http://www.daylilies.org/
Before you buy named daylilies I suggest you look them up on the Daylily Database there and perhaps shy away from the evergreens (Though some will do fine in your zone, it's hard to know unless you know they are growing locally.) I'm zone 6b and I try to buy from sellers in zones 7 up through the colder zones. For me this is mainly due to the rust issue but for you it might means plants that do better in your climate.
Good luck and most of all have fun. Daylilies are a source of endless enjoyment.
p.s. I grew up on the south shore of Boston and I sent a lot of daylilies to my Dad before he died to grow in his rocky New England garden.