Font directories like Dafont typically divide professional fonts between serif and sans serif categories. Between these two options, there are hundreds of free options. However, it can take some care to select the right font. More than a few of the options would fit well for one professional's projects, but wouldn't work at all in another's office. Furthermore, most professional projects require not only upper and lower case letters, but also symbols and accented letters. Before deciding on a font, it's important to double check that it offers you all the characters you'll need.