When I was having my first book cover designed, I was “enlightened” about fonts and copyrights. If you are doing something for commercial purposes – like an ad, you have to have rights to the font.
These are some of the places I get fonts: www.openfontlibrary.org The mission of the Open Font Library is to promote your freedoms as it relates to the use of type. All of the fonts that appear on this site come with the freedom to use, study, share and remix them.
http://www.dafont.com/ – free and public domain ~ and they indicate which. Free is typically free for personal use. Public domain can be used commercially.
http://www.smashingmagazine.com/2012/01/09/high-quality-free-fonts-2012/#more-120954 – free fonts clearly marked whether you can or can not use for commercial use.
http://www.fontsquirrel.com/ – GREAT SOURCE.
Fonts to me are a lot like images – I only purchase images for book covers, product logos, and things like that. For articles and social media posts, I use free fonts and images.