Build Classified ads website?

Hey guys. What do i need in order to build an website like olx or craiglist? Are the premiums themes like ClassiPress any good? I'am a beginner and they seem like a good option but i've heard mixed feedback on that. Are there better options? Then after building the website how do you populate content? You can't just go and copy from ads from other websites(I think?) and starting from zero no one will be interested on using the website. How do you guys think i should approach this?

Anyone with experience with this?

What do you mean exactly ? PM with your detail .

loads of templates on themeforest etc