Earlier quoted context omitted.
RenTec doesn't make money off "buy and hold." They're a quant firm that profits from small inefficiencies in the market, trading that with leverage. Their really good secret is that they have superior data sources, and superior modeling (lowering their risk to almost nothing).
Their secret sauce is less subtle. They harvest tax loopholes [0]. [0] http://www.zerohedge.com/news/2014-07-21/how-rentec-made-mor...
If that's really all they did, it's basically a Ponzi scheme, because they would sometimes lose money.