How do payments work? 

During account setup, merchants are asked to pay a $650 setup fee that includes a minimum deposit of $100 all merchants start with inside their accounts. This deposit is used to pay commissions to affiliates, in addition to the ShareASale transaction fee. Merchants can replenish funds at any time via the Deposit Center.

A merchant pays a commission when a completed sale is referred from an affiliate (there are other actions that generate payouts). The merchant’s account balance will then be deducted, in real-time, the predefined amount (commission plus the ShareASale transaction fee). Transactions that come through from affiliates will be locked and paid out on the 20th of the following month (assuming the merchant account is set at the default lock date).

In a given month, if your account does not generate a minimum of $35 in fees to ShareASale, your account will be charged the difference.

Payment grace period: 

Options to fund a merchant account:

You can find more information here.