Hello, I am starting my own business and I would like to use some fonts on Dafont
But I want to be fair, so I have to clarify some points :
-Is "100% free" okay for commercial use?
- When I download a font that I want to use in a clip; how do I know how much to donate?

Thank You

It depends on the author, so you should ask them.

For a donationware, if no price is indicated in a text film linked, it's function of the quality and the number of fonts included.
I thing $10 to $40 per font is a good price.
But the best is to contact the author.

Thank you very much !