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Pro Free for 1 year (renewable)
StartSSL offer free class 1 (domain verified) SSL certificates.
Con Free disallows wildcard certificates
The 1 year (renewable) free TLS certificate does not allow wildcard certificate and limits to 5 host on a single domain. If you exceed that limit, you'll need to generate multiple TLS certificates.
Con Not trusted anymore by Mozilla, Google, Apple so completely useless
Con Renewing needs manual work and is over-complicated
There is not automatism or script which can be used.