If you are just starting off, please have all of the permits/licenses. And insurance.
You need to know the local laws, regs, governing a caterer. Can you make dishes in your home? I know in many areas that is strictly a no no. And there are a whole lot more.
Having all your legal and insurance ducks in a row, you have to find out what your market wants in terms of food.
Don't assume the 'hispanic' population wants certain dishes, find out. Ask the neighbors, or friends, co-workers. And then come up with an example menu. On that menu you will know the cost of every dish. If they ask for something else you have to get back to them.
The advice about the contract, down payments and the rest two weeks before the event is rock solid.
People get into catering because they love to cook. Most don't like the business part. and that is what they have to learn.
A caterer is a business person first, and a cook second. I know that sounds harsh, but if you are not in it for the fun, but actually want to make money, you need to have a thorough knowledge of that aspect of, well, the business.
Good luck and God bless.
Before criticizing a person, walk a mile in his shoes - then you are a mile away and you have his shoes!