Ask IH: how to launch a job board without beeing unethical?

Hi there!

I would like to launch a job board in a specific niche. I think content marketing and backlink building will be my first marketing focuses, but how can I integrate some first jobs without being unethical trough scraping some jobs from other sites?

And i do want to charge for new postings right from the start.

Hope you can help with some ideas :)