Starting out early!

Who pays for what when?

Who pays for what and when? Does your consulting incur costs that you may have to bear until the client pays? Then you’ll be interested in Gerard’s question:

Hi! I’m 16 y/o and I’m looking to start my social media marketing consulting business. I was wondering how do you charge clients the money that you need to do the work and the money that they pay you to do the work. Do you charge them separately or do you use some of the money they paid you to do the work?
Here’s my answer:
Gerard,
wow, you’re starting early!
I’m not sure what you mean by using money to do the work but here’s my best answer.
If they have expenses that you incur on their behalf to do their job you can ask for that money up front (or get them to open an account with the provider (facebook / linked in, whatever) that you have access to for them and they get billed by the provider)
I bill 40% up front for any labour-related work, and then monthly bills (or on completion, whichever comes first).
You should never be out of pocket on the client’s behalf.
I have known PR consultants who charge 10% on top of any costs they pay for a client.
What do you think? How do you deal with this issue in your own consultancy?