Pass-through expenses

Almost all business's have net income that is a very small % of the gross - and a very large % of  expenses that are 'related' to earning the revenue. You can call them 'passthru' or pasta, but regardless its your cost of doing business, so its an expense. 

If you were a trustee for them it might be different - but you're not - unless the contract specifies that x$ are being held in trust on the customers behalf and are fully refundable.

So all the receipts become your money as soon as you receive it and therefore its revenue and all the related disbursements are expenses. 

If you want to put more lipstick on your financial statements then breakup the revenue into separate lines for services and reimbursements. 

This is a common misunderstanding: "and we use this resources in order to manage their hiring processes, casting and training, etc"

You use Your Own banking and credit card and similar resources. You got Funded by making sales to customers, which gives you the resources. You happen to be paid in advance, which reduces your risk.

@197869

Stated it very well. You should ask your own Accountant if you have a Trust requirement to track this as liability accounting, the same as a law Firm must do. If not, you have Income when you get paid. You have Expense when you Spend funds for business operations, including things that apply to customer needs. Because nearly all of us have this: Gross Revenue reduced by Gross Expense in the reporting.

And this: "I am worries that this will bump our gross income to an unreal amount."

Is not Unreal. You seem to belittle the Size of the business you are now part of. You should be Proud that you have a Huge Gross Revenue!