DaasYochid: Thank you for posting. Very informative. However, I am a little confused by the following sentence.
So, if my very good friend the handyman comes to my home for whatever reason (pick up his son, borrow a bike, etc) and when he sees something wrong with the faucet he fixes it without me asking or even realizing it, I have an obligation to pay him?
If the homeless in the street trhows water at my windshield while I am stop at the traffic light, Am I obligated to pay him?
Where is the line?