There are a variety of services on the Internet that provide free SSL certificates. Relying on SSL/TLS of this kind means that you'll be stuck using lower levels of validation without any support team to get you through manual SSL certificate installs. It's still industry-standard encryption, but you're mostly on your own when using it.
By buying proper (albeit cheapest) SSL certificates from Certificate Authorities specialising in SSL solutions, such as SSLTrust, you'll have entire support teams at your disposal whenever you need them.