It shouldn't hurt you as long as they don't pay for anything until they're ready to have it shipped

1. Foundations & Concealers
Palettes are a makeup artist's best friend. The take up a minimal amount of space and aren't as messy as bottles or tubes. If you already have your cream foundations/concealers, you can melt the product into this empty makeup palette. If you don't yet have your foundations/concealers, here is one that already has product in it!

2. Powders & Blushes
It can be irritating carrying around a bunch of compacts from client to client. There are two solutions for this: purchase already-made powder palettes, such as this powder palette and this blush palette, or de-pot the ones you already have and stick them in an empty makeup palette. For loose powders and blushes, I would suggest storing in these jars.

3. Eyeshadows & Lipsticks
There are tons of eyeshadow palettes to chose from. I would suggest having one of each type. The first type being neutral colors and the second type being bright colors. For lip palettes, here are some good ones. If you already have eyeshadows, you can de-pot them and put them in an empty palette. For pigments and lipsticks, you can put them into this empty palette.

4. Disposable Applicators
When applying makeup to clients, you want to do all you can to keep the process completely hygienic. Disposable eye shadow and lip product applicators and disposable spatulas are great for that. If you'd prefer, you can go with regular makeup brushes and a metal spatula and palette, just make sure to thoroughly cleanse before and after each client!

5. Makeup Case & Brush Holder
You want to first get a professional makeup case, such as this one or this one. Then you want to get smaller makeup bags to organize each type of product into. I prefer clear bags, as it's easy to see which bags are holding which products. This bag and  this bag are good. You will also need a brush holder, and for that I'd recommend this one; it will keep your brushes organized inside the case, and can be wrapped around your wist for easy access while doing makeup.