Copy Classified data from other website?

Hello
I am planning to make a classified website for US and India. I am good in Coding and i have unique concept to represent the clients product with high visibility.

The is Code of website is ready.

Is this possible copy data from other classified and post on my website, Is this legal ?

Or any suggestion to get related data.
I heard some company can crawl data and list on website but i dnt name.