It all depends how much time you can dedicate to it in a short amount of time and how you plan on getting your members into the system.

You could be up and running in Chalk It with full billing support for your members in a day or two.

Are you spending a good amount of time setting up the system (building memberships, class schedule, store, programming, etc) before bringing your members over before launch? Or are you just working on it here and there?

It also depends on the timeline with how you plan on migrating over your members. Are you manually export and importing member information and billing information from your old system? Depending on your system and credit card merchant, that could take a week or two.

Are you asking your members to sign themselves up and input their billing information on their own? That all depends on the members and their promptness.