Hello,
Thanks for the question about Website Down After Installing SSL. It's not necessarily a must-have, but it can be depending on what you're doing with you're website. For example, if you're hosting sales transactions, then you will want to use an SSL certificate in order to provide an encrypted and secure connection. Check out our article called What is SSL and Why it's important for more information. Also, How to Obtain an SSL certificate will give more info if you want to purchase a certificate.
I hope this helps to answer your question, please let us know if you require any further assistance.
Regards,
Arnel C.