Are you going to be making this your full time job or just an occasional service? If it is going to be full time, you are probably going to have to consider what taxes and other expenses you will have...
If you know your work is excellent and impeccable, then you can confidently charge at the higher end of the scale. If you still need to gain experience, lower your sights and do a few free sites for people, or at least at a lower fee, exploiting the publicity the work is going to get for you through word of mouth.
Some people do a cost per page...others work by calculating the time a job takes.
IMHO it is good to get a small percentage of your estimated total when you actually begin the creative process...then decide on pages versus time and either charge all the balance at the end, or break the work down into areas which require a payment at each stage.
I see that some people charge for extra content eg. a photo gallery, a calendar etc.etc. If you have to work on the graphics yourself...you can charge for that. If you have to do proof reading...charge.
Just Google "web site prices" to see what others are charging...it might help you decide for your own tariffs.