Question about categories
In my application of this directory, all categories are not equal. I am in the health field and will have listings from practitioners, schools, treatment centers or hospitals. The price difference of the plan would not be based on "how many categories" but on the size of the entity, i.e. a hospital would pay more than a practitioner. I can accomplish this by adding pricing to each category, and also providing additional listing field appropriate to that category, but there is a problem. Once the listing is approved, the owner can edit the listing and change the category and hence the custom fields. (my idea is to offer a free listing with no custom fields).
Any thoughts on how to prevent editing the category after the listing is live, or another approach to "price by category" (and pay to change)?