Hi Joe,
I am a private tutor though not in your area
. The best thing to do is ask for referrals and email them. Ask the referrals how long they worked with the tutor. Ask how the sessions were run and if the tutor showed up on time and was prepared. Did the student feel like the tutor gave the student enough time to formulate their own responses? This is really important.
While there are certainly many variables in student's improvement, with a bit of effort, most students do better with the tutor. I have had people in the past that did about the same, but that is because they put the same or less effort into their classes. In short, find someone who will be more of a facilitator.
As for price, it varies. I have to gauge how difficult the course is and how much time I put in. Don't go too cheap, bc you get what you pay for! Probably $30-40 range will get you someone good. Also, there are companies that offer private tutoring (more $$). That is a good way to go because they train the tutors, give feedback to the tutor etc.
Good luck, pm me with any questions.