Subscription billing is awesome. But it’s not your only option.Inspired by the growing proliferation of paywall sites, SaaS providers are responding to their call for more malleable billing software. For example, Vindicia just announced that it has added “usage” billing to its billing software CashBox. The software already lets sites receive recurring revenues, but this new addition will allow them to process one-time charges, as well license-based, variable usage, highest-tier usage and flat-fee pricing.While it’s best to try to upsell site visitors into a subscription, one-time and usage billing also allow subscription sites to capture email addresses of more commitment-phobic visitors while also adding to your bottom line. Pay-per-use billing is also a good idea for any subscription sites that are data mining–often researchers need a specific data set for a one-time project. And while these charges won’t keep your cash flow in the black, it will provide you with a list of qualified leads that may be interested in purchasing a subscription at a later date (or spreading word-of-mouth advertising on your behalf).My point? Focus on subscriptions but don’t throw away the low-hanging fruit.