What's a fair split in this type of partnership?

[Jeff Tang]

I have an investor/agent that would like to partner up and utilize my good credit to purchase a flip. Property would be around $500K, with ARV between $700K-$800K. He is proposing to provide the down payment, rehab costs, and PITI for 6 months; I would be the one qualifying for the loan. He's suggested I'd get maybe $25K for my involvement, but we haven't fleshed out the deal entirely. Does this sound fair for a first-timer? How should it be structured? What sort of legal docs should I have setup for this type of deal? Any thing I should be concerned about? Thanks for your assistance!