Is there any way to have a new user pay prior to creating their blog?

Prior to purchasing the ProSites plugin, I missed any mention of the fact that a user had to register and get a blog before they could purchase a blog.

I just discovered this in another thread, and was quite disappointed. I'd been searching for how to set up the sales page, or something like that.

Needless to say, I am quite disappointed. I don't know if I overlooked it in the sales pitch, or if it was not highlighted. This is a significant enough defect for me that I am afraid I may have to seek another software.

So, here's the scenario ... and the question.

My users will be limited to a specific naming convention for the subdomains they can register, and there may be some competition for certain subdomains.

If someone registers a domain name, I do not want it to be "taken" by someone wanting a free blog. I won't be offering any kind of freebies.

How can I keep subdomain names from being tied up by non-paying prospects?

I do not mind them registering first, if they are required to pay, or lose the subdomain name, but it would be more common (and in my mind, accepted) to get them to pay first. After all, when you go to McDonald's, do you demand getting your food before you pay?

Even the upsell, which apparently is the same category as ProSites, is offered and collected on, before the product is delivered.

edit: I looked at the sales page and the only item that alluded to this deficiency was the comment "Offer your users the chance to upgrade their sites and access features ..." An ordinary user would not recognize this for what it is intended to be, a limitation. You do need a more forthright statement describing this limitation.