Why can't you just have someone invest for you and split the profits (and losses) with him?
For one thing fund managers, even fund management companies, own less money than their clients put together. On the whole they simply cannot underwrite 50% of the potential losses of the funds they manage, and an offer to do so would be completely unsecured. Warren Buffet owns about 1/3 of Berkshire Hathaway, so I suppose maybe he could do it if he wanted to, and I won't guess why he prefers his own business model (investing in the fund he manages, or used to manage) over the one you propose for him (keeping his money in something so secure he could use it to cover arbitrary losses on B-H). Buffett and his investors have always felt that he has sufficient incentive to see B-H do well, and it's not clear that your scheme would provide him any useful further incentive. You say that the details are immaterial. Supposing instead of 50% it was 0.0001%, one part in a million. Then it would be completely plausible for a fund manager to offer this: "invest 50 million, lose it all, and I'll buy dinner to apologise". But would you be as attracted to it as you would be to 50%? Then the details are material. Actually a fund manager could do it by taking your money, putting 50% into the fund and 50% into a cash account. If you make money on the fund, you only make half as much as if you'd been fully invested, so half your profit has been "taken" when you get back the fund value + cash. If you lose money on the fund, pay you back 50% of your losses using the cash. Worst case scenario[*], the fund is completely wiped out but you still get back 50% of your initial investment. The combined fund+cash investment vehicle has covered exactly half your losses and it subtracts exactly half your profit. The manager has offered the terms you asked for (-50% leverage) but still doesn't have skin the game. Your proposed terms do not provide the incentive you expect. Why don't fund managers offer this? Because with a few exceptions 50% is an absurd amount for an investment fund to keep in cash, and nobody would buy it. If you want to use cash for that level of inverse leverage you call the bank, open an account, and keep the interest for yourself. You don't expect your managed fund to do it. Furthermore, supposing the manager did invest 100% of your subscription in the fund and cover the risk with their own capital, that means the only place they actually make any profit is the return on a risk that they take with their capital on the fund's wins/losses. You've given them no incentive to invest your money as well as their own: they might as well just put their capital in the fund and let you keep your money. They're better off without you since there's less paperwork, and they can invest whatever they like instead of carefully matching whatever money you send them. If you think they can make better picks than you, and you want them to do so on your behalf, then you need to pay them for the privilege. Riding their coattails for free is not a service they have any reason to offer you. It turns out that you cannot force someone to expose themselves to a particular risk other than by agreeing that they will expose themselves to that risk and then closely monitoring their investment portfolio. Otherwise they can find ways to insure/hedge the risk they're required to take on. If it's on their books but cancelled by something else then they aren't really exposed. So to provide incentive what we normally want is what Buffett does, which is for the fund manager to be invested in the fund to keep them keen, and to draw a salary in return for letting you in[**]. Their investment cannot precisely match yours because the fund manager's capital doesn't precisely match your capital. It doesn't cover your losses because it's in the same fund, so if your money vanishes the fund manager loses too and has nothing to cover you with. But it does provide the incentive. [*] All right, I admit it, worst case scenario there's a total banking collapse, end of civilization as we know it, and the cash account defaults. But then even in your proposed scheme it's possible that whatever assets the fund manager was using as security could fail to materialise. [**] So why, you might ask, do individual fund managers get bonuses in return for meeting fixed targets instead of only being part-paid in shares in their own fund whose value they can then maximise? I honestly don't know, but I suspect "lots of reasons". Probably the psychology of rewarding them for performance in a way that compares with other executive posts or professions they might take up instead of fund management. Probably the benefit to the fund itself, which wants to attract more clients, of beating certain benchmarks. Probably other things including, frankly, human error in setting their compensation packages.