I've never had anyone ask me this so far, but if they did, I think I would tell them how SFI is helping me to grow a residual income from home. And if they don't know what residual income is, I tell them it's like rock stars make when they record a hit record.
They normally ask me for a link after that. If not, I ask them if they've ever heard of Microsoft and if they wished they'd joined them from the beginning.