Visible is a single line carrier. You do have an alternative, for each number or line you will need an account for each, that means for each you need a separate email address for each one. It is my understanding you should be able to use the same form of payment on each one.
With that many lines would you not be better off at a Visible's parent company Verizon or even T-Mobile or AT&T? With that many lines you should be able to get them for $25 a line or less from when I was researching. One thing you need to know, I like the plan and the service here but if you value customer service that is definitely lacking here. If you have a problem with any of your phones service you have no number to call to reach them. You only have 3 options, chat, Twitter messaging or Facebook messenger to contact them. Chat wait times are up to an hour or more. I just thought I would point that out before you dive in multiple lines on multiple accounts.