Non-broker here. How much commission to arrange private sale?

[Borg Lederer]

I am a non-broker consultant who does work (not employee) for an owner of a multi-family asset who wants to sell. I know an interested buyer. 

For my commission, can I or should I split the fee between the two parties? 

I am thinking of charging 3% but should I charge more on a purchase price of 2.4m - 3.4m?