I don't believe there's a standard profit percentage that has ever been set. You'll need to know what your expenses are going to be. ( Your Overhead?) Take into account equipment, travel time, gas and any other costs you may have.
Remember you need to cover your costs and make a profit so just set your pricing accordingly. Something else you may want to take a look at is the going rate in your area, make a couple of calls and get a couple of free estimates on your own lawn and that can give you an idea of what to charge and how much profit you can make.
It all depends on the services that you provide. The national average for mowing is 11%. I found this to be lower than what we were getting over the past 16 years in business. We were closer to 20%. Fertilization programs tend to yield higher profit margins. This could be somewhere around 35%.
