I dont think its mandatory but yes, it is required

It depends on what you are doing and what level of security you want or need. I recommend adding the certificate. The extra cost will be worth it and it will save you from some real headaches in the end.

Yes that is correct SSL on Billing and Ticketing System. If you're using WHMCS it is very easy to use SSL to it. You can also use SSL not for the entire domain but only use SSL when you login.

Just like in Yahoo Mail or Gmail, when you login it uses SSL but once you're authenticated it goes back to the usual HTTP.

Hope that adds help.

Thanks!

IMO, to make a good impression it is a good idea!

All payment systems should be encrypted for the safety of your customers.

SSL should always be used when accepting confidential information. If you yourself are not willing to input personal information into a non-secure form then why would others is my opinion.

It is . Not for you but for your clients. You want your clients to trust you and by having a ssl on your client area to encrypt their ordering process then they will trust you

Not so much for the Paypal, but you want the SSL for the Credit Card transactions for sure. A lot of customers are getting more savey and will expect to see the secure green SSL symbol before they use a credit card. You can get a cheap 8.99 one from NameCheap that goes on just 1 domain that will work perfect for you. No point in spending $69 for an EVSSL.

Well. I would suggest namecheap ssl's too. I use one and never had a problem
But you need ssl even if you have paypal. As i wrote above client want to be secured

If you are conducting any form of business, I bet you will want to have a SSL certificate for your website. The fact that the transaction is secure is crucial to many consumers nowadays since online credit cards theft is pretty notorious.

A SSL will be a lifelong investment for your business.
If you cannot afford a SSL, you should not be managing a online business. Period.