The real question is who is the leader and who is the follower.
If you partner is the leader and you think you can trust him, please do whaterever he asks. You just simply always follow him. Of course, you can give him your suggestions and share your opinions with him.
If you think you are the leader, your partner is the follower, then, you can make the rules how to cooperate.
I don't think the diference of the percentage either of investment or potential lose will make any different at this time point.
So,
first of all: trust.
second of all: always understand the role you are able to play in this cooperation.
Third: do your best to help the leader if you are the follower, or do your best to lead if you are the leader.
