I would do a search for premium classified ads Wordpress themes.

Start there, and build it up.

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Go to themeforest.net and find the best one you want. Try to contact the developer and ask your questions to check if they can support you with custom development.

Hi thanks for your response,

your answers are really helpful for me.. Yesterday I buy a Classifieds Templates with attractive features in Jom Classifieds. And they are ready to customize my websites also.

For More details about Jom Classifieds: https://jomclassifieds.com/

Are you still looking for the company? I'm working with a company which can help you.

Are you trying to make money from the classifieds website you want to create? If so... WHY YOU? Why not any & every other classified ads website out there? How will you compete with Craigslist?

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