I would suggest getting rsvp's for the event, then you will have a general idea of how many are attending.
Renting a popcorn machine is much more profitable than Nachos. Plus, many rental palces will allow you to return the unused packets of popcorn/oil mixture. The popcorn smell makes the event festive, and EVERYONE wants some! ** When you buy bags for the popcorn, be sure to get small bags! A lot of time people get bags that are TOO big, fill them too full, and yoou can't make the popcorn fast enough. No matter how much is in that bag, people will pay a dollar for it!
Nacho cheese is messy, it takes a long time to heat up if you have to open a second can, and the chips, for it to be economical, come in Big boxes, so you end up with a lot more waste at the end, and therefor less profit!
As far as pop, It is worth it to buy from a place that will allow you to return full, unopened cases. Pop only has about a 6 month shelf life, and it will go flat if you hold onto it for another event.
We have a school of 600 kids, and we find that it's MUCH more profitable to buy powdered lemonade, and make it ourselves, and sell it by the cup. Again, you can make it quickly, and what you don't use of the powder, can easily be used for many other events.
