A much newer system with a beautiful backend interface, Growsumo went through Y Combinator recently and has mostly modern Startups as its clientele. It does not yet manage actually paying out, like most of these systems do, but it does track how much you owe affiliates, and then you could just pay your affiliates with Venmo, Paypal, a check, or whatever you want. It’s definitely the most elegant of all the affiliate systems we’ve seen. No upfront costs, they just charge 3% of the value of the account gained from the system.