WordPress recommendations

You could create a custom post type, but it may not be necessary, depending on if the existing page and post types will have their own dedicated purpose or not. The decision to use one type or the other might also depend on how you manage who can create, edit, or publish what. If you use some sort of membership plugin, you may need to work with what types the plugin supports. Or it might support any type.

Data related to any post type beyond content, title, and other posts table fields, will be either a taxonomy term (like tags) or a custom field. Custom fields are good for data that is unique to a particular post. Terms are good to help you better organize posts by a common characteristic. There is a sizable gray area where either would make sense. For example, state. Name OTOH would almost certainly be a custom field. Unless you want to save distance from a fixed point, you’d probably be storing the franchise geographic coordinates as custom fields. Queries would get franchises within an arbitrary distance based on a range of coordinates. The actual distance would be calculated on the fly.

On the topic of distance, calculating accurate distance between two coordinates on the earth’s surface involves very complex ellipsoidal geometry. But for most applications, much simpler spherical geometry can be used. The inaccuracy introduced is typically not very substantial. An average error of 0.3% I’m told.