Just a suggestion... 

A good affiliate system needs to be tied to your payment system - that’s how you track commissions, account for refunds, distribute checks/transfers, avoid fraud, etc. Depending on the payment system you use, you may be able to use one of the 3rd-party affiliate services - like ReferralCandy, Referly, etc. Chargebee has a few integrations available that plug in to their payment process. 

Even a good affiliate module on UNA side may not be sufficient to cover all the needs of a robust affiliate tracking system, so if it is a crucial part of your strategy, definitely look for a complimentary service.