If anyone can provide a link for me to go in the right direction for my situation below, it would be greatly appreciated--I have been searching for answers for days and no success.

Here's my simple plan:
I want to perform my services for clients. As part of my fees, I want to include ONE FREE MONTH of membership lessons, and then have it convert to a $20/mo. fee.
-HOWEVER-
I would like to offer regular sign ups for people who just want the membership lessons, without giving them the free month.
How would I go about doing this??
Thank you SO much for any assistance in advance.
Jaime Buckley