First of all: Last warning. Let's keep things clean, polite and above the belt or this thread is done.
OP: You don't seem to understand the concept of building a portfolio. It's not something you get to do on the backs of paying clients. It's not even something that you normally get to do for free. It is usually something that costs you money, sometimes a lot of money. I wouldn't want to think of all the studio rental fees I've paid, gas I've bought, etc, etc, just to bring in a model for a "free" shoot so I could add her to my portfolio
This is true whether you're a model, photographer, MUA, or dog-groomer! You have to be able to demonstrate to potential clients that you can produce the level of work they require. In order to do that you have to show them images. Go home, spend a couple of hundred dollar, buy some food and photograph it. Nothing exciting, canned soup, a slice of cake, cookies on a plate, that sort of thing. Put together a portfolio of ten images which show that you can light and present food decently and then shop yourself around.
Telling the potential client that his idea won't work is one thing, pulling out a binder of high-quality food images and showing him what you can do under the right conditions is another animal entirely.