You should have excellent php working knowledge and motive to finish workable project.
Need setup php script with add few feature as per requirement.
Read script description and suggest.
1. User system:
There should 2 more user type.
a. Author work as team member and take care of particular location listing, means can add/edit of particular location listing.
b. Subscriber - Only can add/edit own listing. Claim Functionality available. So when claim approved by Author or Admin.
2. Google Schema for Local Business and Google SEO Meta
This is local business listing. So All business listing should as per schema and validate by google schema tool. Its most important.
Listing should have unique seo meta title. You can insert postID in each seo title.
3. Guide for Import and Export Listing through sql/phpmysql.
Note: Pls not think/suggest for wordpress. Already running on wp few other's classified site.
Need on native php for scale up listing to million. WP is not suitable.