This is always tricky. I recommend that you take your own photos where possible.
I have an account with bigstockphoto.com and I buy photos there (around 1 or 2 dollars each. There are other stock photo sites.
Also, have a look here https://blog.hubspot.com/marketing/free-stock-photo-websites
and here https://www.studiobinder.com/blog/best-stock-photo-sites-for-creative-agencies/