I guess billable would be ok if I was taking half. And half of the markup on parts.
Or maybe we could do a straight subcontract and you could forget about benefits and I will supply my own van and parts and I will give you 10% of billable time only. But if I'm busy with my own customers I will give your customers(soon to be my customers) a window when I will be there.
Let me discuss it with my calculator, I will get back to you.