Affirm gives you a flat percentage interest rate ranging from 10 to 30 percent depending on what you're buying. The service's signature feature (aside from real financial functionality on a mobile app) is up-front and clear disclosure regarding how much a purchase will end up costing you. Today, his company has extended that feature to a mobile app, functionally creating a virtual credit card for anyone who wants to trust a tech company instead of banks. Paypal co-founder Max Levchin launched Affirm back in 2012 to extend credit for folks to buy things online.