I need help

SO we have an inventory part # set up for our labour - it is NON Physical - 

I need to know how to set up a proper sales department for when we invoice customers for labour - I need the standard cost for the labour to come off the price we are charging our customer.

I called BV and I could not get anywhere......what accounts do I need in the sales department and what group do I attach to the accounts.....example

sales revenue being $100.00 - however we have a cost associated with it being $50.00 - HOW do I set the sales department up correctly ...I am totally lost on this one.