If you're getting your full rate, let your friend enjoy marking up your services. Make sure he's paying you promptly though, not paying you after he waits for t

If you're getting your full rate, let your friend enjoy marking up your services. Make sure he's paying you promptly though, not paying you after he waits for the final client to pay his invoice, so specify he's your client in the contract and that he's comfortable paying your invoices in a time frame you expect not dependent on the final client paying his invoice. Maybe he will bring you other engagements, you could even outline this in your contract with him that he will actively market you to his network. Finding projects isn't trivial, it's mainly relationships and who you know. If he can keep bringing you projects I'd enjoy the ride. Maybe let him know that for future engagements like this you're increasing your rate if you think you need to increase it.