Whether the subscription cost is 1¢ or $100, making the first payment is a pain. It means getting your credit card out of your wallet, filling in all that information, including all those numbers on the front of the credit card, the expiration date, the CCV number on the back—it's just not a fun process. The nice thing, of course, is that with an ongoing subscription, subscribers need to do this only once. After that, the payments should be automatically taken from their credit cards each month (or quarter, or however you decide to bill).
So, that first payment needs to be made as easy as possible. Fortunately, since you won't likely have to worry about a shipping address, you can keep the forms relatively short. You can also work in price discounts depending on how long they want their subscriptions to run, with monthly subscriptions being the highest price, six months (paid in advance) being less expensive on a monthly basis, and a full year (also paid in advance) being the least expensive, on a monthly basis.
Perhaps the allure of running an e-commerce site has gotten you excited, but the thought of putting the site together, getting the merchant account set up, and managing and shipping your inventory gives you a headache. I don't blame you! It's a lot to do. Fortunately, there are options that allow you to profit from e-commerce without having to manage your own store. You can use a common store that will sell your products for you. You might not make as much, and you'll still have to do some pretty robust marketing, but you'll be able to make money without having to invest in building your own site.