Adam
There's a big difference in what is a decent percentage and what you can expect.
I've spoken to 2 or 3 firms in the last year and all they were offering was 35% !!
In addition they were charging low prices, it worked out that you would be working 8-10 hours a day to earn the same as you could with one job of your own.
In my opinion, you would be better off spending the time trying to build your own business, even if it's leafleting or cold-calling.
Steve