Social Media

Hi, I have a website and I want to ascertain if something is possible regarding social media advertising. I own a real estate website and I want to encourage people to share my properties on facebook, twitter and other social media platforms. I will reward people that do this if a property sells because of a referral to a friend or a friend of a friend or a friend of a friend of a friend etc. Lets assume that i share a property on my facebook account to 150 of my friends and i try and get them to do the same and so on through many levels of friends. Lets assume for a second that this went viral until eventually someone who sees a picture of the property wants to buy it. I will need to know which friends to reward for introducing the property. This reward could be paid through several friend connections or levels like a multi level marketing scheme would work. Is it possible to track who first shared the property and track the path through to the person who eventually decided to buy the property ?? I guess we can track who shares the property initially as this will be shared through our website but how can we track who is sharing once people start sharing and liking through the social websites themselves. Please advise. Thanks Chris Scott