That's a tough question. Even tougher is the answer. Realtor fees are usually around 6%, so $12K on a $200K home, $30K on a $500K home, and $64K on a $800K home.
Since you're living in Orange County, my guess is that we're talking about a $500K to $800K home. While a nice gesture, I don't think $3K to your friend will do the trick. You'll have to figure out what matters more to you, friendship or money.