How much would you charge someone to clean up water leak in condo?

I help out a family friend from time to time cleaning his condo when he is not able. He is out of town and I went there today to clean up and found that the condo above him had a water leak (it was her icemaker) that leaked into his condo. There was water dripping in the kitchen, down through the cabinents, onto the floor, above the fridge (so there is water all under/behind the fridge) The leak continued out into the hallway where it is carpeted. He would like for me to clean it up before it molds since he will be out of town for 5 more days. Obviously he won't be paying the clean up bill. (the upstairs neighbor will) So what is a fair price to charge for a clean up of this nature? Would you pay by the job? By the hour? I want to be fair- I'm not in it to make money, but I would like to be reimbursed for my time. I'm guessing it will take 2 of us about 4 hours to clean it properly. thanks for your input :)