Magento Affiliate extension by Magestore
You can choose the commission type to be fixed or percentage and easily add the preferred rate. Besides, you can differentiate commission/ discount levels of the first order and following ones.
You are also able to set “payout requirement” which is a specific amount that referrals’ balance must reach before they can request to withdraw money.
Another feature that is also very interesting is that if you suspect your affiliates’ reliability, you can choose to hold their commissions in a period of time.
Finally, once an affiliate has succeeded in referring a friend to your store, he can be entitled to the whole-life commissions from that friend’s transactions. For example, when a Customer is introduced to buy your products through affiliate A for his first time and through affiliates B, C the second time, third time, etc., this feature can allow you to add commission for A only.
You can view more detail here: http://magentoaffiliateextension.com