Background:  I'm a volunteer for a small local government unit in the United States, and due to budget issues we have no funds to develop a website.  Hence, I'm an unpaid volunteer for the government office, working with free, opensource software (mostly wordpress and free templates), in search of a free hosting provider; within a few weeks we will have a local benefactor donate the money to purchase a .com domain name.   
I noticed on the account registration page one can only register once and registration information cannot be changed once registered.  I have not registered yet for this reason.   
Question:  Do I need to wait until we own a domain name first, then register?  Or can I register for a subdomain first (like "example.heliohost.org") then later add the domain name (like "www.example.com")?     
Prattle:  I've used a competitor of yours in the past (think 10 multiplied by 11 megabyes on a commercial tld) when I would design and donate free websites to non-profits in my local community (free minus the cost of their domain name), but it's been about 2 years since I've last designed a "free as in lunch" website, and the greater restrictions they've placed on free sites coupled with their move to a monthy versus 1 time upgrade plan has moved them out of reach for this kind of work.  Looking around for another free host, I first found one, but their registration page has been broken/down first at least half a month, which has caused me to be concered about their claims of great uptime numbers.  Several review sites sing your praises, so I'm glad to have found a hosting provider which I hope will become an invaluable resource to non-profits and public interest/local government organizations in the future.   
edit to add section headings so the question stands out better for quick reviewers   
I'm still trying to answer my own question, and think I may have - on the FAQ it says:   
    
So I assume so.  I also saw in mega-huge letters, underlined, that said futher down the page "please provide your username and domain name upfront" though now that I read it that appears to only apply to requests for support and not registration.     
But I'm still not 110% sure, based off what the registration page said (make sure info is right - can't change later).  Any clue would be greatly appreciated.