Each of our subscription plan levels will allow you to configure up to a certain maximum number of products and includes a fixed allocation of download-storage space on our server; your total usage must fit within both of these limits, so e.g. if you aren't using all the product slots available for your plan but need more space, you'd need to upgrade to a larger plan that includes more space. Products and space are unlimited during your initial 7-day free trial period, so you can set everything up, and then when you're ready to subscribe, you would only be offered plan levels that can accommodate your current usage.
To economize on your storage space needs and subscription cost, our digital-product plans of $18/mo or higher would also include our Remotely Hosted Downloads feature, which allows you to configure Single File Download products with a Remote Product File URL for the file's location on your server, rather than uploading the file to use space on our server. Files stored remotely on your own server would NOT count against your plan's storage allocation on our server. This help page explains more about how our Remotely Hosted Downloads feature works:
http://www.e-junkie.com/ej/help.file-downloads.htm#remote
Regardless of whether you upload the file to us or host it yourself remotely, the download links we issue would be unique to each buyer, cloaking the "real" URL of the file, and expiring after the number of attempts/hours (whichever comes first) that you specify in the product's settings.