Is it important to activate SSL (and buying it) when limiting to use DEMO file?

I just installed zc 1.5.1 and would like to make practice before actively using the system.
I would prefer not to buy an SSL certificate before my commerce is active, but I would like to know your advice concerning security of my site and zencart system, or , if you know a way to protect zencart system while using it "internally", thanks

SSL has nothing to do with the security of your Zencart installation. If it has value, it's in the fact that information sent from your customers to your payment processor(s) is encrypted.

Test all you like, then when you're ready to take the site live, buy and install the SSL certificate, if necessary.

If you ask sensitive information from your customer like credit card no. etc on your website then ssl is require to secure these information from hackers.