Have you considered speaking to an existing caterer and offering to work for and with them to get a full picture of the catering business? If they are in agreement, work out a contract and timeline so they won't think you will grab all the information and walk away.
Tell them you want to work in all areas to see the business from the inside out. After all you need to know how to do something in order to train others.
You may have to search around to find a company to do this with you but I will bet there is someone out there who will look at this as a challenge and take you on.
This will give you a good picture of the entire business.
Have you thought about buying an existing catering business?
I'm a business broker and you would be surprised to learn that it's more affordable to buy than start from scratch. If you have limited funds you can negotiate a deal with seller financing or go to bank of america for an sba loan.
Happy to help you if you have more questions.