Quick question about invite-a-friend

Been multiboxing a while, just have to make accounts that are actually owned by myself now.

I am under the understanding that using this feature gives you a free month of game time on my main account if they (me) upgrade to the full version of WoW "and pay for their first month of game time". But since the first month of a new account is free, does this mean that i have to pay for the second month in advance to get the free month on my main account? I'm upgrading online in order to not have to go to the store to buy more copies of wow since I am only using a single install.

The friend has to pay for at least one month over and above the first free month.

I believe the way this is worded, once you pay for your 2nd month (after the 1st free) on the new accounts, your sponser account gets the free months.