He said it can't be a 50-50 thing.?

He is my friend. He brought up an idea and i embraced it. The idea is turning out to be a successful one and i told him we need to open a joint account with two signatories cos contributions has been equal. Later he told me that i should tell him my percentage in the business if it works out and i said its a 50-50 thing. He said no that i should re-think about it. What do you think i should tell him cos i'm down psychologically.