Fundraisers are often paid a percent of the funds they raise, though the fundraising organization is often hesitant to have that be publicly known. I have seen rates as high as 50% of the monies raised – but would hasten to add that the most well-respected non-profits would not see that kind of “commission” as appropriate.
Another consideration is the level of aggressiveness you want in your fundraiser – the more risk and upside you put into a comp plan, the more urgent and aggressive your fundraiser is likely to be. For small-donation type fundraising where the number of calls dialed (or doorbells rung) makes all the difference, it can be an effective strategy.
Those pursuing more substantial donations (thousands of dollars and up) often find more success with having some of their largest donors involved in securing additional donations on a volunteer basis. People with large amounts of money to give usually ask some tough questions about exactly where their money is going – and would like to know that almost all of it will go to support the cause to which they intend to donate (vs. the fundraising effort).