I was wonder what is the legality in using freeware fonts in a product that you sell?
Depends entirely on the font. You would need to check with the maker of the font.
It also depends on the nature of the product, whether it's in print or in PDF (and within the PDF category, some licenses allow you to use it as long as you don't embed it in the PDF). All free fonts come with a license that will spell this out.
You should also take care to verify that you're using an honest-to-goodness free font, and not a ripoff clone font whose outlines have been copypasted from a font you would have to pay for.
I don't know an easy way to do this, unfortunately, but it's just the nice thing to do - think about the typographers.