What is a fair split on this real estate arrangement??

[cwsiggy]

My sister and her husband bought a house with a friend of theirs to add on and flip. The friend is providing all of the money from another state and will have nothing else to do with the construction and labor. My brother-in-law is providing all of the construction expertise (he is in construction management) and crews etc. He will also be joining in on the labor as he has time. What is a typical fair deal for the split on the profit when the house sells? Obviously, both parties are needed, but we are thinking that it should be at least 60% Brother-in-law, 40% financier friend. Maybe even 70%/30%. Any ideas.