Or you could just buy gallons of lemonade form your local grocery store., cut fresh lemons, pour into a dispenser with spigot, and sell for $3 per 16oz cup.
If your going to do it, do it right the first time. I`ve seen lots of cups of lemonade thrown in the trash because some yahoo fills a clear, 5 gallon glass jug with Country Time, throws a dozen cut up lemons in it for display, and pushes it out the window bragging its fresh squeezed. Get real. People aren`t stupid. You give a customer the best dang lemonade on the block, you`ve got yourself a walking sales person advertising for you. When I started out, did the same thing. Been there, done that!
War story: trailer next to me was using County Time. Young lady walked by complaining about the taste. Ask her over to my place, took her cup she just purchased, threw it in trash. Made her a REAL lemonade, fresh squeezed. No charge. What did she do? Told her friends how good my ade was. Walking bill board. Put it in a clear cup so everyone can see it. Put a cherry on top. Use strawberry puree. Brightly colored straw. Be different. Good luck.