Contacting customers through the PM system is totally allowable, so long as that contact does not include advertisements, promotions, or solicitations for work.
That is your own interpretation.
I'm a single-man operation, and there's no way I can compete with companies making millions of dollars a year when it comes to web design and advertising expenses.
Then compete with thousands of other "single-man" operations. Elance.com, Freelancer.com, Odesk.com among others are your friends. Most of those freelancers don't have their own websites or advertising budget, either.