eBay ( EBAY) is another payment card network that's got tailwinds lapping at its back. I know that may sound funny at first glance. After all, eBay is best known for its namesake auction site. But eBay also owns PayPal, a payment company that's quickly becoming eBay's biggest earner. Right now, PayPal contributes around 40% of eBay's total revenues. A couple of factors make PayPal a disruptive force in the payment business. For starters, PayPal boasts more active users than some of the second-tier payment card names, giving it a huge pool of users to sell merchants on. Because PayPal has focused on the online payment business for so long, its foray into payment systems at brick and mortar stores is a big deal -- that new source of transaction volume could materially boost the firm's revenues. The novelty factor of paying with PayPal at a physical retail location doesn't hurt either. eBay's other businesses are no slouch either. The firm's auction site is still a major earner -- and complementary online marketplaces like StubHub round out the picture. By being on both sides of auction transactions (eBay caters to both buyers and sellers), the firm has found a lucrative business catering to small business, with everything from shopping cart software to invoicing platforms. Investors should appreciate the fact that eBay tends to focus on entering new markets that are instantly monetized -- unlike some of its conspicuous tech sector peers. A spotless balance sheet with a deep net cash position rounds out the picture for this Rocket Stock. Keep an eye out for earnings on Friday.