you're always competing with the person who'll try to "copy facebook for $15/hr"
once you've got more than one customer you'll inevitable get in the situation where, if you were honest, you'd have to tell Customer A that his project is late because you've been working on Customer B's project. If you are honest, Customer A will freak out and odds are 50% or so that he'll dump you right there.
I joined the project management institute, and one day looked at the code of ethics I signed onto and I realized I'd be violating it all the time if I was doing typical freelance work for the typical freelance client.
So I won't.