Thanks for reaching out to Community. I'm happy to provide you some information on running two companies in QuickBooks Online.
You can have more than one QuickBooks Online company (account) with the same email address.
With that being said, you're able to have as many company files as you want with the program however, with QuickBooks Online you'd need to purchase an additional subscription for each new company file you create.
If you have any more questions or concerns, feel free to drop a line. Have a great weekend!