When you open up the service to the public, do you plan on having a little counter or something showing the available spots open, or E-mailing those people who pay to let them know they'll be activated once you setup a new server?
I'm just thinking from the new customer perspective that I'd be freaked if I paid and didn't have immediate access to my account. Since you're using PayPal, you might get an unnaturally high charge-back rate if they didn't understand before subscribing that they'd have to wait.
I'd hate to see you have your account Frozen because of that.