I'm a college professor who teaches writing, and someone suggested to me that I should offer individual tutoring for the SAT writing test as a small side business. I don't live in the DC area, so I'm not trying to solicit business here!

I would just like some unbiased advice from parents of college-bound high school students.
1. If your child has already taken an SAT prep course of some kind, do you feel he/she would benefit from additional writing instruction?
2. Is the writing portion of the test regarded as more difficult than the math or reading sections? Or does it just depend on your child's individual strengths? The person who suggested this to me was saying that the SAT grammar is really tough, but I wasn't sure if everyone has the same perception.
3. I'm not a parent myself, but it seems that most parents would hire tutors based on word-of-mouth referrals. Does this seem right? Any suggestions for how a new tutor could go about building up a clientele?
Any other comments are very much welcomed. I haven't decided if I will pursue this or not; I'm definitely still in the researching stage.