Ask HN: Monthly vs Annual - Subscriptions.
Trying to decide how to launch a subscription model for my web service. Monthly or Annual?
The CC processor we use (www.braintreepaymentsolutions.com) {and I'm very happy with them} allowed us to apply for annual billing after we had many months (7? 8?) of billing under our belts, and they could see that we weren't super risky.
So, yeah. Look at different scenarios, but recognize that it might not be up to you at first, and adjust your expectations and projections accordingly.
You're pretty much stuck with monthly, or charging yearly in arrears at this stage.