Plan what you can temper or cut ahead of time. (Maybe you don’t need gold leaf on the site tokens)
Be aware that prices can change over six months (especially food items) and let them know you know.
Be aware that low bid does not always mean best bid (portapots should NOT lock from the outside.)
Lookout for hidden charges, like delivery and pick up charges or cleaning charges.
Keep a spreadsheet of anticipated items and cost for both site and feast.
Finally, how much are the attendees giving you?
Compile all of your costs for the site.
Prepare a rough budget for the feast.
Estimate how many people you think will attend.
Decide (probably before now, if you have a good Feast Steward) how many you want to feed.
Are you going to have reduced fees for children/youth or a family cap?
Do the math… how many feast fees do you need to cover the cost of the feast and how many site fees to
cover the cost of the site (and other requirements for the event). Now you know where your profit starts.