It depends on the dentist. If you do not have insurance, then each dentist fees may differ. Some will give you a 10% discount if you pay in full. If you have insurance check what your copay is. MOst dental insurance cover preventative at 100% (no copay) others have copays that range usually under $30, but it depends on your plan.
If you do not have insurance I would recommend you to look for a dental discount or private insurance plan. Many dental plans are not too expensive and it will save you money in the long run.
For a very first visit you can probably expect to pay $100 - $150 depending on the dentist. This is because a new [patient exam is more extensive than a regular check up. After that the check ups could range from $60-100. If you do not have insurance and can't get it, you should be able to find a dentist that will work with you on payments.
I would highly recommend you finding a pediatric dentist, and not a general dentist. You'll find the experience with your child much more pleasant.
Good luck!