Back in 1995-1996 I certified on all the major processing networks. Back then, mail order was the closest business type as e-commerce was not a thing yet. Today, i just offer PalPal because they offer PayPal, PayPal Credit, Debit and Credit Card. The savings, to utilize a processor is not worth it for me but I could see a world where processor and/or credit card gateways are used. Hence, I will add your choice for free if you allow me the time to integrate your choice. That time cannot be clearly defined right now but I can say it involves contacting them, finding out if what they offer is compatible, reporting back to you, designing and writing the code, testing. It can happen very quickly or I can get bogged down at each step. Or something in between. The good news is Ihave done it twice so I am fairly aware of whats involved.