Since your site is hosted for free, where will it generate revenue from?? Advertisements!! Yes, advertisements get the money needed to keep the websites running, but, what type of ads will be displayed on your website, you will never know or be aware of.
Chances are very high that your site might have malware or virus content in those ads and become a point of threat to visitors. This loses the reliability of your site.
Hacking is a dangerous threat to any website. When in business do you want to lose your personal information and credentials to those hidden thefts??