Paypal is one of the best ways to do online transaction because it is most popular trusted platform for online transaction.
SSL(Secure Sockets Layer) is one type of protocol which transmits information in secure way within encrypted code via internet between client and website server.
You can also get SSL certificate from it’s brands authority or from reseller of the SSL certificate also. Purchase of SSL from reseller will give discount on the certificate but if you will go to buy it from brand authority you will not get discount on SSL Certificate. Because reseller buy them in bulk. Don’t worry regarding certificate quality because either you are purchase it from brand or reseller they are issued from the brand itself.
It depends upon which type of SSL you want to purchase as per your website requirements like for single domain, sub domains, multiple domains etc. For more detailed information regarding type of SSL certificate and its purpose refer this link http://kb.wisc.edu/page.php?id=18922