Just figure out how much food/drink/etc. that you need and then price them. If you have no amount of money to start with at first, then you have to plan what you need!
I am new to this, but to start out, As I ubderstand this; you first find the amount of folks you will be serving, say an example; 200 people.
Then come up with a simple but fun menu, then hold the amount of selections to a few.
Do not give the Customer total control of this part, ask them what type of food and what they are trying to acomplish. Then suggest based on what you really can do. You and the Customer decide on the final setting and theme and menue items togeather.
Then you figure the amount of each of the serving portions, like (example) a meat dish,
for example; say it will be 6 oz servings per person , so 6 oz's x 200 people = 1200 oz's, thus you turn that into pounds and price it at a local meat wholesaler.
ex: 1200oz / 16 oz/lb= 75lbs, so you would try to get the best price on 75 lbs of what ever meat- or- (chicken, pork, fish etc...) that you are serving, and determine your price per serving from that.
this is a very ruff example, and also for a very large group or party, but I hope it helps.
You would have to figure this for each item you need to complete the entire menu.
And make sure you take on events for the size you can actualy handle. if you can only accomodate 25 folks, say that.
I found that when Starting out it is better to gain experience than get way over your head the first time out.
I'd start with a very small menu that you know you can acomplish, keep it simple and down to a few items, not a lot of dishes. Keep it colorfull with layerd flavors to make it interesting.
And Do what you know you can make well and have experiminted with and have had sucess, knowledge of and complements on.
Try to control this part tightly. Beter to have 3 good items, maybe one 3 course meal, instead of a menue with 25 separate dinner items on it!
Keep it simple and unique. The more personal it feels to the guest the better. make them feel special. Keep a theme for the entire meal.
You have to ask your customer a lot of questions to learn their tastes and feel, and what they like and want. once you have this info, then figure protions, sizes, your costs and from that give them an accurate estimate, do not guess at it.
Be honest as to what you really can do and can not do with the customer. Do not B.S. them to talk them into the job. It will show immediately if you did that.
My wife and I have had not much experience, but when we did this- (ask and be honest) we had excelent results- best wishes.
also ask if there are any known medical problems for any of the guests, like allergies, diabeetes, heart etc...
better to know ahead than be sued later!
once you have all the portions and have priced it wholesale, then if you have no money...ask for a down payment, make it enough to cover buying all the food and preperations , the wholesale price...
then you can bill the customer for the remaining monies after the service is performed.
one way we did it, was this way, after the night was over we left the customer a special baked cake in her kitchen, (no charge), and a thank you card, and folded the bill and placed it in the ebvelope with the thank you card next to the cake.
We keep the price right to the estimate, no changes and it went over very well.
it's a long answer, hope it helps