Ask HN: Should I keep this Job board for free or sell it as a lifetime deal?

HI folks, I've been in the data space for 12 yrs. I launched https://databirds.co to help people in data space to find their dream job.

I have a few ideas/doubts running through my mind. Please suggest which way is good?

1) Is the current niche good to start (Data Science, Data visualization, Data analytics) or is it too broad and I further niche down to Data Visualization (my core area) alone?

2) Should I keep this to one country (USA) specific or global?

3) Should I pre-vet the candidates so it saves time and gets quality candidates to recruiters (USP)?

4) Should I sell it as a one-off $1000 lifetime unlimited jobs deal? or a $99 per job?

5) Should I keep it completely free to post, but a small revenue from employer-sponsored banners or resume writing service for candidates?

6) something else?

Please let me know your thoughts.