I didn't think you took it that way just wanted to be sure.
I personally feel that if you're going to cater on at least a semi regular basis, there's certain
equipment you should acquire ASAP, provided you can afford it and have means to store it.
A stock of 8qt chafers for one, either economy or nice ones, maybe a cambro (thermal carrier)
or two, say one for hot one for cold. Other things....the less you have to rent the more you can
incorporate that savings in both $$ and time into your profit.
There are 2 major ways to figure your rate--the going rate (risky) and cost plus.
Which can also be done a couple ways-- cost plus an added x factor like times 3 or 3.2 etc. (also risky).
But the best way is to calculate (all as accurate as possible) your food costs, your fixed costs,
your event specific costs, your planning time, shopping/prep and cooking/serving time, extra labor,
then your desired profit, to yield a price per person.
And you need to decide your minimum. Mine tends to run at about 50 people or so-- under that and it
stays the same.
So its not only specific to your own costs, but is also influenced to a degree by your location.
Here in LA county for instance my going rate for events I've done similar to this with one helper,
disposable serviceware, and a 1 hour chafer serve would be about 14.95 to 16.95 per person.
That might sound high to you, maybe not.
But remember that this being your first event will "set the scene" for your future rates.
If you doubt that....well trust me, it will. It's far easier later to adjust your prices downward
through discounts, specials etc than to raise them, even under the reasonable sounding excuse
of inflation/cost of living.
Also not that there are MANY great threads in here on this very thing going back 14 years--put in
a search for Catering Price/pricing etc.