A profit margin of between 25 and 30 percent is acceptable, but not excessive. Add that rate to the estimated hours your customer will need. This way, you can determine how much you should charge per project or down payment. You want your customers to be happy with your work.
Next, consultants should check with their competitors to ensure that the profit margin does not exceed 25-30 percent. One important thing I've discovered is not to talk about hourly rates. Instead, you should talk about margins and margins. As a consultant who does 1099 jobs through my company, I always declare that I allow a profit margin of 15% on my services.