title: Reccuring payments ambiguity
body: <p>I have a class for recurring payments for subscriptions and there is a thing that is not 100% clear for me.
  If I initialize an order with following params:</p>
  
  <pre><code>Amount: 25$
  Initial amount: 0
  Period: month
  Freq: 3
  </code></pre>
  
  <p>Does this mean that the user is paying 25$ three months from now or does he pay 25 now with no extra charge (initial amount)?
  In other words, what I am asking is - is the initial payment some extra charge or can it be used as a advanced payments for the first cycle subscription, in which case, the params I would need would be:</p>
  
  <pre><code>Amount: 25$
  Initial amount: 25$
  Period: month
  Freq: 3
  </code></pre>