Even for commissioned work: CONTRACTS!!!
They're there to protect both you, and the commissioner. Look up a work-for-hire contract template online and adjust it to your own needs. Oh, and make sure the commissioner actually reads it properly too, it should be a two-way thing.
If you want a team to help you out, all the better! That's really awesome, but yeah, contracts are everyone's friend as long as you know what you're doing. 