The question is what will be an appropriate equity that I should ask?
Ideas are worth absolutely nothing, try selling one. Don't worry that it's his idea, the idea SHOULD and WILL evolve as you develop it, and the idea will then be both of yours.
Money obviously has value, but at this stage of the venture, it's too early to size it. He should loan the money to the company in the form of a convertible note (giving him a nice return on his money) and valuation will come down the road when there's more transparency. You should each split 50/50 the equity, with him holding the debt. Anything less would be unfair to YOU.
Let the equity vest based on hours worked; that way, if one of you goes from 20 to 60 hours, it's much easier to figure out how that works ahead of time.