Why can't you just have someone invest for you and split the profits (and losses) with him?
At this point the cost of borrowing money is very low.  For the sake of argument, say it is 1% per year for a large institution. I can either go out and find a client to invest 100,000$ and split profit and loss with them. Or, I could borrow 50,000$, pay 500$/year in interest, and get the same return and loss, while moving the market half as much (which would let me double my position!) In both cases the company is responsible for covering all fixed costs, like paying for traders, trades, office space, branding, management, regulatory compliance, etc. For your system to work, the cost to gather clients and interact with them has to be significantly less than 1% of the capital they provide you per year. At the 50% level, that might actually be worth it for the company in question.  Except at the 50% level you'd have really horrible returns even when the market went up.  So suppose a more reasonable level is the client keeps 75% of the returns (which compares to existing companies which offer larger investors an 80% cut on profits, but no coverage on losses). Now the cost to gather and interact with clients has to be lower than 2500$ per million dollars provided to beat out a simple loan arrangement.  A single sales employee with 100% overhead (office, all marketing, support, benefits) earning 40,000$/year has to bring in 32 million dollar-years worth of investment every year to break even. Cash is cheap.  Investment houses sell cash management, and charge for it.  They don't sell shared investment risk (at least not to retail investors), because it would take a lot of cash for it to be worth their bother. More explicitly, for this to be viable, they'd basically have to constantly arrange large hedges against the market going down to cover any losses.  That is the kind of thing that some margin loans may require.  That would all by itself lower their profits significantly, and they would be exposed to counter-party risk on top of that. It is much harder to come up with a pile of cash when the markets go down significantly.  If you are large enough to be worthwhile, finding a safe counterparty may be nearly impossible.