Marketpress & SSL - Do I need SSL to use Marketpress with Authorize.net or PayPal

I purchased Marketpress a year ago for a client that has lagged getting running... so they are finally moving forward. I'm going to set up their Marketpress for PayPal initially while they get Authorize.net approval. Do I need to do something about SSL? Right now they have a basic hosting package with Simplenet. My understanding was that Authorize.net didn't need SSL because the transaction will take place away from the website, but I need to know for sure if that is true. What is the safest way to setup a Marketpress shopping cart?
-k