How do people charge for Interior Design projects?

I have started advertising my services as an Interior Designer and Consultant, and have started receiving inquiries and requests to help in home decor. I was curious as to how others charge for their services in the field? Do you charge by project, hours, strictly subjective based on wants of client? Any... show more I have started advertising my services as an Interior Designer and Consultant, and have started receiving inquiries and requests to help in home decor. I was curious as to how others charge for their services in the field? Do you charge by project, hours, strictly subjective based on wants of client? Any information would be really helpful. I have advertised as working with clients designing, going shopping with them, etc. I am trying to be really flexible, but want to have formal rates to add to the legitimacy of what I want to do. Thanks.
Update: Do some people not charge for initial consultation? Also, I believe one client wants help in designing/furnishing their entire house. How do other designers address this?
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