The fee calulations are like much else - sound easy but the devil is in the detail. I have seen many many different scenarios, 2 and 20 is pretty standard, 2% on total amount managed - leverage included usually to take you to a notional amount of assets managed. Then the 20% can come pre or post the 2%, and is subject to a highwatermark, which are almost always set in stone although i have seen managers try and reset these every year. if several strategies are being run, fees are usually netted between them, and management on the total.
they are usually paid quarterly but accrue monthly, so only monthly new highs are paid out on. other things to consider are money added after the initial investment, and what happens to incentive fees on additions of capital from an investor if the allocation has dropped due to performance.
it would be best to hammer out these details early, and with a lawyer...!