How does Envato manage referral incentives?

Hey everyone, just looking for some incite on how Envato manages their incentives for the referral program. I’m looking to add referrals into my own site, but I have to think about how it could lose me money. Looking at Envato, it’s clear they don’t have many problems with their system.

I’ve been trying to run through possible scenarios where users can abuse my system, and so far I’ve come up with a pretty major drawback to a referral system that offers incentives:

On the marketplaces, when you refer a user, you get a percentage of their first deposit, or first purchase. Cool, that requires a bit of money to start off with, every business does, no problem. The problem I see with this is, what if a user registers 2 accounts, refers one of them through the other, and then deposits $100 on the referred account. The first account now has $30, and the second, referred one, has $100. Now if the money is withdrawn for both, the user has $130 now. How does Envato stop this? Do they track deposited money, and not allow it to be withdrawn?

Can anyone think of any other solutions, and/or scenarios that could be a problem? I wanna get this right so I don’t risk myself money.

First account $30 can be withdrawn but second account $100 can’t be withdrawn there need to spend to purchase items.

First account $30 can be withdrawn but second account $100 can’t be withdrawn there need to spend to purchase items.