I am presently involved in a small hedge fund and have a few observations:
The fee structure is usually as follows mgmt fee of 2% per year paid quarterly on assets under mgmt at the quarter start (addiions pro-rata by invest date). On a $2 mio fund that's $10k / quarter. Performance fees are 10-20% of high-water mark profits. Reach a NAV high and trade under it for the next three quarters, no performance fees (and likely lower mgmt fees as people pull assets away).
The big players in funding want to reward consistency - they want a low SD of returns, high Sharpe ratio, no surprises either way - so they structure the deal this way.
For example, let's take a proprietary mechanical trading system that has results (actual or hypothecated) showing an average monthly rate of return of 3% with an SD of +/-.4% over some reasonable time frame. They get their funding and start trading the program. If the fund returns aren't close to their expected results, the principals will be called in to explain why. If the results are significantly higher than prior testing, the funders will want proof that the risk parameters haven't increased. And if returns fall, well maybe they'll have another quarter to straighten it all out. This is h-o-t money, it moves in and out faster than one can imagine.
Triple digit returns are great - heck, high double digit returns make me giddy - but those returns almost certainly correspond to greater variance in returns.
And that's the deal breaker. It's also the pain in the backside factor; nobody bugs you when the variance is as expected and positive, but string together two bad months in a row and your phone won't stop ringing. Trust me, I have been there and it isn't fun...
If you could develop a program that returned a constant 3-4% per month with tiny variance over 5 years of trading real money, the institutional funders would throw all their money at you, hand over fist.
With regard to structure, offshore is the way to go; nearly none of the big guys are on-shore (open to US investors).
It may be better for a start-up to incorporate as an LLC and register in his/her state and the federales as an investment advisory firm. If assets and number of investors stay under some figure there's minimal paperwork.