Ok, I have no idea how to do this startup but it seems very profitable. Have you ever noticed how anyone under 40 believes with 100% certainty that social security won't be around for them when they retire.
Well I think it probably will be around. Most big (popular?) government programs aren't going away no matter what the media says.
So how about selling social security insurance. Buyers pay a premium each month to buy the insurance. And if social security isn't around when they retire the insurance pays out what they would have gotten from social security.
---- Edit ---
People don't think the insurance idea is viable so let's turn this idea on its head. The company goes out and buys the future social security benefits (or some portion thereof) from individuals ands pays them say 10 cents on the dollar. People who don't think SS will be around think they're getting free money, and the company makes a bundle if SS stays around.
Heck, could the US government could be doing this to fix social security?