Frankly, if you need money fast, then don't sell subscriptions. People pay much quicker and faster if it's a one time fee than if it is a subscription - what you then have to do is that once a year, you bring out something so compelling, that the users are willing to purchase another 'chunk' one time.

After trying the subscription model, and noting the pains the users would go through to NOT have to pay a subscription fee, I switched to a fixed one-time fee.

It makes you work harder to have something new each time, so that the users go through the upgrade cycle.