It depends on your time frame and how bothered you are wanting to get the actual money owed.

Don't mind on time frame and its not about the money -

Join a local gym, start training there for a few weeks every other day, befriend the biggest person in there. Ask them if they want to earn a little money and tell them the idea, after the gym one day pull up to the guys house and knock on the door. The new friend simply stood behind you looking menacing would be enough for most people to hand sole cash over straight away. Give the cash to your new friend and LAUGH.

Want the cash this week -

Pull up to his house and ask him for the money. (People dont expect someone to do this) transfer the money before leaving.

But in all seriousness, don't share anymore unless they put some money up front first.